Punisher has a great post--plenty of things to do. Also, if the problem is the bar then goblet squats and dumbbell squats held at the side are possible options--if its the compression then that will help, as will zercher squats. If it is something else causing the bulging and pain then changing to those variations won't help--however: prowler, sled drags, and other options like that are great.
If 135 causes you pain I don't think reverse bands will help you too much, as that's about the lowest weight you can handle on a bar.
I would work on the underlying causes.
In the meantime: glute bridges and hip thrusts, GHRs both manual and on the machine, slideboard hamstring curls (one of my favorites along with GHRs for hamstrings with a general prep phase athletic application) are all options for posterior chain work along with the more standard stuff like leg curls and back extensions, good mornings (questionable but if they are pain free then do them), reverse hypers if they are pain free--but play with the execution to see if there's a best or worst way to avoid.
You also have bulgarian split squats, lunges, reverse lunges, step ups, farmer's carries, sissy squats, and a whole host of other things you can do for training that don't require spinal loading.
You also have ways to load them: superset, pre-fatigue, post-fatigue. You don't have any problem training legs or building more muscle.