For the questions.
1) Get rid of the pain. We train to live better, not to suffer.
2) Yes, around 85kg. The pain was there at every squat and then all day and all night. I honestly though I had broken a bone. A physiotherapist diagnosed a weak piriformis and gave me exercises that made the pain much worse. He suggested accupuncture, I said "Why not?" it did nothing at all. I stopped squatting for a month. The pain got less. I fixed my form, the pain has not come back like that. I get some warning pains, I check my form.
3) It's probably all technique.
I am not an SSC. I can see.
You are looking straight ahead.
Your back is quite upright.
Your stance may be narrow. Shoulder width is a starting point. Some people need a wider stance, some people need a narrower stance.
Knees seem to be a long way forward.
I think your knees are still travelling throughout the squat. You should touch the roller in the first third of the squat and you knees should stay there.
4) Maybe not very much. When I squat, people run and hide because there is so much noise from my joints that they think there is gunfire.
5) You seem perfectly mobile and you can get into the squat position. You really don't seem to need more of either.
6) No idea
7) You got rid of the pain before. I think that if you fix your form, you can go ahead without getting it back.
Rip says in the book that hip problems often occur for novices after about three months of training. From issues are allowed to develop as the weights get heavier. From errors and heavy weight produce problems.