Sounds like a good list of things to think about. I'd just re-emphasise the importance of vitamin C. Eating fruits is not, unfortunately, going to give you anything like what your body needs. Linus Pauling, one of vitamin C's greatest champions, did a lot of research in this area. He said that if you look at the natural proportions in which other animals' bodies manufacture their own vitamin C, then in a similar proportion we should be getting 3-10 grams a day. Maybe at one time in our history it was possible to get this from food. Certainly not today, because the fruit and veg available to us are depleted in vitamins and minerals due to over-farming. (Organics have more, and I'm not honestly sure what you'd be getting if you grew your own.)

Infections and low immune responses seem to have figured prominently with you, so getting that vitamin C would be the first thing I'd do. I'd go easy at first because some people who have been poorly for a long time find that it's a shock to the system.