That's my man right there! Nice squatting. Lol
Knees out, chest up, great depth (more than needed even), good speed, etc. I have the same issue, I go very low in my squats and get the buttwink like you. Don't need to go so low and it will help with the buttwink but I just feel a better groove hitting my normal depth.
As RogerThat pointed out, the thumbs over grip is much easier on the elbows. Some people have mobility enough to do thumbs around and that's fine but I always do thumbs over even with over 400lbs. Your hands are t meant to support the bar. You may feel like you don't have control if you switch your grip but the bar is held up by your upper back muscles and bones. The hands simply make sure the bar stays pressed against the back.
If you want to switch do it gradually. Try it out on warmups and then add it in to working sets. If you feel off switch back but keep working at it.
Another thing to help the elbows is tripping the bar as wide as possible. I hate the feeling of doing so and always keep hands close even though it flares up my elbows. I just feel too loose.
If your gym ever gets a buffalo bar or cambered bar you can also use those if elbow pain is an issue. Just run a macrocycle or two with the bars and switch back to an Oly bar 6-8wks before a meet or max testing l