You have done an amazing job with your nine year old and I can fully appreciate how difficult things must be, but clearly if you can get the diabetes under control life could still be good for both of you (at least
for a few more years possibly). I would encourage you to keep trying
for as long as you can. The injections are more a nuisance than painful (as a diabetic I can actually say that), and if he is otherwise contented, then it must be worth persisting.