Shoulder Restrictions

Hi everyone,
I was after some pre-hab advice

I recently went through the ‘neanderthal no more’ post on T nation, and realised how poor my posture is. I particularly noticed how rolled forward my shoulders are.
I am pretty tall (6’4) and have to spend a lot of time working on low surfaces which doesnt help.

I find on overhead press I tend to lean back wards towards the top, which I assumed was me trying to ‘cheat’ the weight up, but now am thinking it may be that my shoulders struggle to actually roll back enough.

Ive also just started doing shoulder wall glides (back to wall, arms against it and slide arms up and down) and was a bit shocked at how hard I found it, my lower back was desperate to curve forwards to allow the movement.
I also found it a lot harder than anticipated to simple stand with arm at 90 degrees to body, forearm pointing up against a wall and hold it.

I’m going to start doing these ‘stretches’ more often, and some rack pulls with scapular retraction.

I was just wondering if anyone had any other suggestions as to stretches/exercises that may help?

Many thanks!