Physical fitness + disability; any suggestions?

Google seated exercises - there's a lot of stuff you can sitting or leaning against a chair.
Gentle yoga/pilates/tai chi might also be good, in small sessions, maybe 10-15 minutes at a time.
Listen to your body, and feel if your tolerance for exercise increases with repetition - you might be able to work up to harder/longer sessions over time.

When my ankle gets too painful to do anything I grab a large bouncy ball and use it to work out with. Raise it above your head, twist to each side, bounce/dribble it, throw it above you and catch, lean forward/backwards holding ball out or up, balance with ball on one hand and raise opposite leg. Use your imagination and combine moves. It's not high impact but it keeps you moving and can improve balance and coordination.

It's great to do in front of television too.

Kettlebells are another thing I use as well.

I'm not sure what HMS stands for and why or where you hurt, but in addition to the water exercises, pilates and chair exercises, using a recumbent bike at the gym may be beneficial- over time you can gradually increase your endurance; you can keep track of the time and intensity that you do so that you can gradually increase it. Also, one of the little peddle contraptions (sometimes called an ergometer or a restorator) can be used with the arms while seated, with the ergometer on the kitchen table. You can also use that with your feet as well. That's a relatively inexpensive piece of equipment. There are also elastic bands for strengthening that you may be able to use as well.

You can do crunches and bench press with dumbells laying in bed, You can do seated rows and Marine press with dumbells while sitting in a chair. The things you can do with resistance bands are limited only by your imagination