Nosox, welcome to the forum. Your commitment to finding the best sweetener for you and your mother is very admirable. I'm very impressed by the number of sweeteners you've sampled in search of the right one.
First of all, I can't stress enough the importance of combining. When you combine certain sweeteners, a synergistic boost occurs, giving you more sweetening power than if you used the sweeteners separately.
In other words,
1 part of sweetener A + 1 part sweetener B
doesn't equal 2 parts sweetening. It's 2.5 to 3 parts sweetening (some will even say 4). Because of the sweetening boost you get, less quantities of each can be used, resulting in less yuck factor. Combining magnifies the sugary taste of the mix and minimizes the other qualities.
Which to combine?
Well, it depends on what you're making. If you're making something where the textural/bulking qualities of sugar are needed, that's going to require a completely different mix from a dessert that just requires sweetness. If you require caramelization, that's an entirely different playing field. Humectant or crystallization qualities of sugar or corn syrup - everything requires a different approach.
With that in mind, there are a couple of popular combinations that seem to work fairly well in most baked goods.
Liquid Splenda
Liquid Splenda is the top of the heap. As you've noticed from putting it in beverages, in small amounts it's one the least offensive sweeteners out there. It's also relatively cheap and easy to obtain. For this reason, when people combine sweeteners, this is usually the lion's share of the mix. I recommend the Sweetzfree brand rather than locarber, as it's cheaper, faster turnaround and, being undiluted, less likely to be contaminated. And no, I'm not saying this to get the free ounce
The biggest problem with liquid splenda is that it provides no sugary bulk/texture to baked goods.
Erythritol
Erythritol is number two in my book. Besides providing the bulking textural qualities of sugar, it's has almost no blood sugar impact and very few carbs (12 net carbs per cup). It also has no digestive issues associated with it like the other sugar alcohols, as it travels a different pathway through the body. There are also reports that it caramelizes.
It does have the cooling effect which puts off a few people and is very expensive. Combining it with liquid splenda helps to offset the cooling effect quite a bit, though. The two have an excellent synergy as well.
Ace K (Acesulfame Potassium)
Ace K is tricky stuff. It doesn't have a completely clean bill of health, and has an aftertaste that offends a great deal of people. It has a phenomenal synergy with splenda, though, so extremely small amounts can be used with great results. A lot of popular products are based on the ace k/splenda combo- diet rite soda, waist watchers, and carb countdown milk, just to name a few. Unfortunately, pure Ace K is extremely expensive and almost impossible to find. So, to utilize ace k in your mix, you have to go the diabetisweet route, which brings isomalt into the picture, which, in turn, brings up the topic of sugar alchols.
Non Erythritol Sugar Alcohols
It looks like you've done your homework on sugar alcohols so I'll refrain from writing a book
Sugar alcohols have a tendency to be big question marks when it comes to carb impact, caloric impact, as well as laxation threshold. Laxation threshold is serious business, especially when you're baking for others. It's one thing to make something for yourself that could give you diarrea, but making that decision for someone else is a tricky area. Although I've seen charts on laxation thresholds that seem to correspond to how I react to them, response can be a very individual thing. That's the biggest problem with sugar alcohols - you can have all the charts/figures in the world but until you consume them, you really don't know what they're going to do. Everyone seems to react differently.
If you're able to test your mother's reactions to different sugar alcohols (glycemically/digestively), that would probably be the most prudent route. If not, well, I would avoid non erthritol sugar alcohols altogether in the desserts you bake for her. That may be overly cautious, but until the fog surrounding these things clears a bit, I think cautious remains the way to go (when baking for others).
For yourself, since you haven't mentioned any digestive issues from SAs and you aren't diabetic, then I think you have a little more leeway to work with them in very small amounts. I would stay away from using Maltitol, especially since you've noticed that it's stalling you. Other than that, I would rely on the sketchy charts/figures that I mentioned earlier to guide you. Some people don't respond according to the stats, but many do (I personally do). So, work with the SAs with lower glycemic 'stats' as well as keeping an eye on the laxation threshold numbers. In other words, no maltitol, and definitely no maltitol syrup (glycemic). No mannitol or lactitol (laxation). Other than that, it's up to you. Some people attribute wonderous health benefits to xylitol, which I have yet to see substantiated. It is a good sweetener, though, and seems to be a popular addition to a splenda/erythritol combo. Isomalt appears to be in the same general realm and provides some sugar like qualities that the other SAs lack, such as 'glassing' for candymaking. The other aspect of isomalt is that it's in diabetisweet, which, as I mentioned is the only known source for Ace K. Sorbitol is another of those middle of the road SAs. When I started on this WOE, I purchased sorbitol since it was cheap and available locally. It's been producing great results when combined with splenda, although, from a stalling perspective, I'm not really sure. Whatever you choose, keep the SA content as far down as you can, since they all have the potential to stall.
The throat irritation, btw, will go away. It happend to me when I had maltitol for the first time (sorbitol too).
Fructose/Fructose Containing Products
I have heard the same negative health reports regarding fructose. The stuff is bad news for the general population and even worse for diabetics. Whey Low (a fructose based sweetener) is popular with quite a few people, since it acts/taste 'just like sugar.' I've wholeheartedly tried to understand the claims whey low makes regarding the safety of fructose and I just can't connect the dots. I've even spoken to the president of the company on the subject and I still can't come to terms with their claims. The burden of proof regarding the safety of a company's products lies on the company, not on the customer. Fructose is dangerous stuff. Until whey low can prove without a shadow of doubt that their product is safe, I say buyer beware.
Stevia
Lastly, if you are truly committed to finding the best sweetener for you and your mother, I would recommend spending the big bucks and trying some stevia. Everyone seems to have their favorites, but I seem to notice that three brands get mentioned the most:
Nunaturals sooolite
Now White Stevia powder
Sweetleaf
At the moment I'm not going anywhere near stevia. I was in love with sooolite for a while only to find it inconsistent. Having encountered too many thoroughly vile brands of stevia and getting unreliable feedback online and from friends, I just can't gamble any more money on the stuff. The one huge downside to stevia is that even though it has synergy, a bad brand will ruin your baked good, even in a small amount. If sooolite resolves their consistency issues or another brand develops a strong following, I may give stevia another shot. Until then, no stevia for me. Stevia seems to be a very personal thing, so you might want to give it a try. It might be okay for you.
So, where are we? Out of your current sweetener collection, I'd play around with the following proportions (for your own use):
Liquid Splenda (40%)
Erythritol (20%)
Xylitol (20%)
Diabetisweet (20%)
Remember this is all based on sugar equivalents. You don't want 40% liquid splenda by volume. You want to convert everything to it's sugar equivalent and then calculate percentages. And don't forget that there is a lot of synergy going on. Whatever recipe you make I'd always start with 75% of the recommend amount of sweetener and taste as you go.
Also keep in mind that this is only a rough sketch. Different recipes will require their own unique approach. As recipe specific issues arise, feel free to post your questions on this forum.
You'll be dirtying a lot of measuring spoons/cups, but the synergy going on should give you a nice pure quality of sweetness.
For your mother, well, hopefully you can talk to her about the potentialities of xylitol and isomalt and do some testing, as liquid splenda combined with erythritol is good but not as superb as with the other two.
I look forward to hearing your results.