Do you stand over extended too?
You reached your body’s tolerance level for being over extended.
You need to take a look at your technique and rebuild.
Carl Paoli has a good progression on the Cody app Freestyle MoveStrong 1
Rebuilding the foundation aspects will start to address the other technique deviations you are experiencing.
Squatting below parallel is not the cause of lumbar tucking.
Lot of skill, drill, technique with your mobility work.
To address the psoas you need to address the movement patterns/posture that is making it tight.
Episode 75: Your Inside Psoas Bits, World Record?
Episode 129: The Twin Bowstrings, the Psoas and Scalenes
Jill Miller Smashes Your Guts! (and psoas, and tacked down viscera, and matted down abdominals…) Part 2
Episode 26: Hips and Seppuku: Psoas and Hip Soft Tissue Mob
Episode 40: USAW Oly Prep: Some New Hip Love /Psoas/Calves
Bubo Barbell Pec/Psoas Smash Quicky or What to Do With Those Bent Barbells

What are you doing to address the inflammation in the area?