Crickets are fine. What I mean is the "carnivore" care has protein. Since he's already eating crickets he doesn't need the carnivore one. It would just add more protein and he'll get enough from the crickets. You want the herbivore blend so it will have more of a veggie base than protein. There's a couple choices on that site.
He does need greens more than protein at his age. But honestly the only reason for critical care is for calories and vitamins. I think you're already providing what he needs now that you're giving vitamins. But then again he went many years without vitamins so the added boost might be good for him. It's really up to you. Since you can get him to eat you don't need it so much. If you decide to get some you could mix a little in his smoothie.
If he can fit in the hide it should be fine. He'll go in it if he needs to. One of mine hasn't used his in months. I wouldn't worry.
There really isn't a need to bathe them unless they are dirty or they enjoy their bath. Maybe once a week if you really want to. Some like to drink in the bath or use the bathroom too so it really depends on the situation. If you suspect impaction then a warm bath is good too. Bathing is not a necessity though.