Well, I got Boone as companion and on my way to Nellis he got crippled. He can't be healed with stimpaks because it says he has full health, he won't use the ones I put in his inventory, he never seems to sleep because if I sleep he doesen't get healed, and I can't find an option at a doctors' that helps him. How do I get him to be.. You know... Not crippled, again?

Hmm... Try getting him hurt then use a stim on him, or if you are not on hardcoe, find an "accidental" way to knock him out, then he should be good as new

Find a nice easy fight, and win it. That may correct it. I had both EDE and Veronica hobbling round for a while with unfixed injuries and I wasn't going to waste a stim on them. A couple of powder gangers sacrificed their lives for the greater good.

Can you give him a Doctor's Bag?

If not playing hardcoe mode: Get them 'killed'. Veronica (My only human companion to this point.) always comes back with full health/not crippled after being unconscious.