If your squat problem is knee or back related, I recommend checking Ben Patrick aka KneesOverToesGuy and his programs. I'm not affiliated to it by any mean but I've been a paying customer for a year and a half and his method of training has been life changing. My knees and legs are now robust and bulletproof, they used to be weak and painful
His approach to shoulder training might be of interest too if one of your injuries is shoulder related
Which doesn't make its success less impressive though but people might want to know that