I have a bad back, neck and shoulders situation going on as well, so much so that I did a bout of physical therapy for it. I mainly do stretches on a stability ball (such as making "T, I, W and Y" shapes with my arms) and push ups. I also try to stretch out my arms while standing them out by creating a "T" and pulling backwards as if I'm trying to pull my shoulder blades together. Lastly, a foam roller helps bring me relief and if you're able to afford $20 or so you can order a long, dense one off of Amazon.

Please let me know if you have any good tips as well because I would like to increase my ability to survive sitting for longer periods of time, haha.

Wow thanks for the fast reply. I feel for you man the pains sometimes unbearable. That foam roller looks/sounds interesting I'll try that.

To be honest, my tips aren't that good. All I did is to exercise (Train my back and shoulders) and put a pillow between my knees when I sleep since I have a bad posture while sleeping. And of course try not to slouch while sitting.

Please let me know if you have any good tips as well because I would like to increase my ability to survive sitting for longer periods of time, haha.