You sound like you’ve done an amazing job so far, you’ve been supportive throughout and I know how hard this can all be so that’s no small feat.
I think only you can decide where you go next. If you carry on supporting him as you have then that’s great, if you feel like you need to take a step back for a bit then that’s also fine. There’s no shame in walking away temporarily (or permanently for that matter) .
You may well end up doing this for a very long time. Whether you do or not is up to you, it’s one of the few things you can control in this situation.