Heycal......from what you described, your posture is begging for Supine Groin Progressive using the wood tower shown in the video I linked above. Regardless of what else you do to help your back, that is likely going to be a significant help to you.
You're spending a LOT of time online searching around for an answer. Presumably your time is worth something. One option is to just go to the NY clinic, purchase an individual visit, see if it helps, and after 2 weeks if you don't think it's taking you anywhere, get your money back and go do something else. But the odds are good that you aren't doing the ecises you specifically need for your unique situation, and you are likely not doing the exercises correctly, which will mitigate their benefit.
Both were true for me when I tried working from the book, and for virtually everyone who walks into my clinic who tries working from the book. Many people get significant benefit nonetheless, but when the generic stuff in the book isn't working (as was the case with me), then the issues above are likely the reason why.
Foundation is cool. I've got the guy's book and have done most of his exercises. For certain my of my clients I've recommended his stuff and it's been very helpful. For other clients of mine, if they tried to do his stuff they would not have a positive result. Their bodies are just functionally unable to perform the movements.
if you want to dabble in it, go do a youtube search for 'the founder', it's like their core flagship exercise. Watch the video, study the form closely, then give it a try if you think your body is up to it and see what happens.
Volkl Organix V1 Pro
Pacific Gut 17 gauge mains at 54lbs/MSV Co-Focus 17L gauge crosses at 50lbs