Thanks for your kind words. I am not a medical professional so I can only point to things I have discovered along the way.

TOS is the hardest thing that I have faced in my life and has completely dominated it for the past six years. I am in my late 30's & hence I have had to do my own reading to come out with fixes.

Your abnormal first ribs are a structural defect - those need to be fixed for optimal results. But suppose we look at it the other way, if you have bad posture and those ribs, yet you weren't in pain, what changed? I would suggest your computer work which pushed your neuromuscular system into overload, stressing some muscles and letting the rest "switch off".

For the obvious shoulder part

If you have a long neck, chances are that your clavicles droop downward (do they? check the angle at which your collar bones are- do they point downwards and/or are flat) and you have a stretched upper trap and your scapula are positioned lower than they should be (droopy neck, depressed shoulder syndrome).

Typically, the dominant arm (right for most of us) is more forward and downward/than the other one (that's normal). However, if both scapula are lower - have a PT check this, then chances are that your following muscles are overactive:
-Upper Traps, Levator, Rhomboids - with Upper Traps likely being weak as well
-Weak/Inhibited: Middle Traps, Lower Traps, Serratus.
What this means is when you attempt to raise your arms up, your scapula are lower than they should be, and rotate out upwards too much (leading to shoulder instability, and compromising the space through which nerves travel near your neck).

So how to fix this? Your PT should help with the exercises and you should do them gradually.

For the not so obvious part

Take a look at your posture. Is it tilted? Do you tend to favor one leg over the other & do you hyperextend your knees? Do you have a lordotic or swayback posture?

Typically, posture begins from our base, the pelvis. If you can gently, by relaxing muscles elsewhere make subtle changes in your system so your head no longer needs to go forward, it might take some of the strain off your ribs and shoulders.

Stuff to explore.