hi and welcome. Are you buying everything from the vet? You can get syringes from online and local pharmacy for a lot cheaper. Only a handful of states require a prescription for them. Walmart is the cheapest place I am finding syringes, meter and supplies for the meter right now. Also the wet cat food to along with coupons. I am thinking automatic pet feeder might be a good idea for your cat to do portions through the day if you could separate from your other cat?
Ideas for exercise- laser pointers seem to work well, harness and leash walking works for some cats not all, about 30mins of activity a day should help.
How much are you paying for insulin now?