As far as your squat goes have someone watch you or video yourself watch for any spinal reversal. Just keep yourself honest in this area.

Tight hamstrings can be a motor control issue. If you have someone around that can check your active straight leg raise (FMS) and toe touch. If you can easily touch your toes with a rounded back but score poorly on active straight leg raise its not in your hamstrings. Chances are that your hamstrings are getting tight as a protective mechanism. They may also get tight as a counter to excessive tension in the front of the hip. So keep the anterior chain supple as well.

Work on setting your hips back a little more and play around with your hip hinge movement. Dan John and Gray Cook have good stuff in this area.