Sounds like a situation where you need help from someone else.
You have have something else going on.
Is there a coach your can have help you? Or a friend?
You’ve tried to address it on your own and aren’t seeing improvement.
There are a couple reasons for this.
You aren’t addressing the cause of the problem, you may not be doing the best mobilizations for what you are working on, you may or may not be doing them correctly. The situation didn’t happen in a day so its going to take time to improve.
Where you see the issue may not be where the issue originates.
How many times a day are you working on it?
Shorter sessions more often throughout the day help especially in the beginning.
Minimum of 2:00 to see change. This is a minimum you may need longer with certain things and if it is an issue you have had for some time.
Mobility and stretching are not the same thing.
Minimum of 2:00 for each mob in problem areas.
Until you see change or until you stop seeing change.
Lasting change with a problem area will take more than 2:00 in some cases.
Some are ok to do before a workout some as post wod lonly.

What is your standing and sitting positions like?

Yes, there is alot of MWODs and it can be confusing. It is important that you have a working foundation in the terms used, equipment, and techniques. You can start from Episode 1 which is a good way to start. You’ll see each aspect as it was introduced to the Project.
I would recommend watching the webinar The Athletic Shoulder: Anatomy, Physiology & Function for more information on how the shoulder works and how to start looking at shoulder function.
There are episodes that hit the low back
Pro Episode # 43 – Pro user Request Friday: Snatch, Sotts & Torque
Pro Episode #17 – Down Stream Of The Over-Extended Athlete: “Spondy” and Training

Low Back Ache, Back Pain – Quick Test | Community Video
Episode 168: Simple Recipes for Fighting Common Back Pain