Hi Brona,
I'm assuming you've taken the carb count of the cauli froma US book or site - total carbs includes fibre while the nett or digestible carbs are all you have to count for dieting. However, beware, as the fibre is already deducted here and in UK, so if the label says 5 carbs, it's 5 carbs!
Fat consumption is a debatable issue - if you're on Atkins, most purists say you shouldn't cut it back as it helps satiety and has no impact on blood sugar. If, however, you find that your cholesterol goes up by a whopping number and stays up, it might be appropriate to cut back a little. This is a contentious issue and you really need to examine everything as it affects you and the programme you've chosen. I low carb to my own plan and don't worry about fat, but YMMV. I suspect that calories overall DO matter, though, so you need to 'weigh' it all up and decide!
I DO have a recipe for both pastry and crumble - the problem with rhubarb is the ability to get it sweet enough. I mix crushed Splenda tablets (much lower in carbs than granular) and the herb Stevia, which I got from US - this seems to help by a synergistic effect to make it sweeter. I also add ground coriander - absolutely gorgeous spice for rhubarb, so orangey.
I will search out my pastry and crumble recipes and post them tomorrow.
Babs