Wow, it looks like you have a lot on your hands. Sorry to hear that your son is not well.
Maybe try those training tooth brush with silicon bristles and let him 'brush' or 'chew' on it when you bath him. Use those toothpaste that he can swallow. For now, get him interested in brushing first.
Or you could try the tooth wipes if he really won't let you brush. (I think it's 'Spiffles' or something like that. Watsons and Gaurdian have. Kiddy palace have too.)
Kids all go through a phase where they won't eat this or that. My girl went thru a phase where she won't drink milk. My boy still going thru his phase of not eating meat. The idea is to keep trying and hope the phase passes soon. Try to get a pretty plate and separate the diff. food items (try about 3-4 types) for a meal. (Eg: a small lump of bread, a small portion of fruit, a small portion of cheese.) Then see what he eats/tries. Sometimes, it's colour, sometimes it's texture. Feeding kids ain't easy. And just cos he will only eat cheese this wk, dont't get excited or worried. He might decide next wk that he hates cheese now and will only eat apples.
I know it's hard, but try not to worry too much. At the end of the day, if he's hungry, he'll ask for food. (Not worrying is easier said than done. :P I still struggle with this everyday.)