slipped discs

Due to a work injury 10 years ago I have four bulged discs. At the time I weighed 155 and squatted 375. I’m not 28 and squat pain free at 350 and climbing. My question is, is there a limit to the weight I can squat before my back just gets really messed up? Also, are there any exercises good for that region? Anything for slipped discs?