Is weight training an option (or are you already doing it)? That can go far towards ensuring what you gain is largely lean mass, and exercise might also help to increase appetite, if that's an issue.

The lower carb nuts are restricted on Atkins mostly for fear of weight gain, if weight gain is desired, I don't see any problem with some of the better options. I would lean towards lower carb options like macadamias, walnuts, pecans.

I don't know what medical condition you're recovering from, but if you're avoiding carbs for any reason, cashews are a bit carby, pistachios are a bit better, but still fairly carby for a nut.

That may be more protein than you need, but unless there's something about that medical condition that would benefit from lowering protein, (say if being in a deeper ketosis would be therapeutic, for example) I wouldn't worry about it being excessive.