I'm no doctor but that doesn't sound very definitive. Definitely could have some minor venous or arterial TOS though. If your arms aren't swelling or changing colors and you haven't gotten a clot it might mean you have caught it early. Compression of veins arteries and nerves can happen at many locations from the neck to the shoulder. Pec minor can be a big culprit as well. I would talk to your PT about loosening the muscles in the neck, (scalenes, SCM, mostly). You want to loosen the muscles in your chest, primarily the pec minor, and you want to strengthen the back muscles, lots of pulling like rows, shoulder retraction with bands, etc. Your pt can help with specifics. It is important to get the muscles to relax before you do a big regime of stretching strengthening. This is the protocol I am doing now.

It seems like you gain an inch and lose and inch but you have to rejoice in small victories. To "cure" TOS it's a change in the way you move, it's a change in the way your body works. I would talk with a throwing coach and see how you can work on your mechanics as well. As you know throwers and people in overhead sports like baseball are at an increased risk for serious issues with TOS. It is the nature of throwing and the violent movement in that area from the neck all the way down the hand. You must be aware of posture 24/7 and keep shoulder blades back and down like you are trying to put them in your back pocket.

Good luck, I'm perusing around. Not a lot of people around here anymore it seems.