Hi again,
Thanks for the added information, video link.
It is frustrating for both of us that I cannot just reach out and treat the problem for you.
The added info sent reinforces my opinion that you have a number of problems, all of which should respond well to simple but very specific treatments.
1. The ache in your arm is probably due to a sub deltoid bursal impingement, but may include a small intrasubstance tear in the supraspinatus tendon. That is not a complete tear, but a small section that has a defect. Direct pressure over the bursal region and supraspinatus tendon where it can be accessed may ease the problem. Cortisone injection for chronic cases may be required, but give up to 12 weeks for recovery if you go down this path. Scans to ensure no tears in the tissue could be undertaken, ultrasound not that accurate at times, Wikipedia reference-linkMRI better but expensive. The exercise I sent is a better bet once the initial deltoid bursitis is addressed. The symptoms include grab through range - a painful arc of movement 80 through 120 degrees of the arm out to the side. Another symptom can be an ache half way down the outside of the arm.
2. C6-7 nerve root compression will give the tight cord feel down the arm to the wrist, into the chest and shoulder and possibly the neck and head (behind the eye and across the head).
Mobilisation of the neck as previously described, with levatore scapulae stretches are likely to decrease the arm pain.
3. Sciatic pain, hitched hip can be caused by the piriformis being tethered. You may also have a mild Wikipedia reference-linkSIJ irritation as well. Deep tissue massage of the piriformis then gluteal and hamstring stretches are done for a few days.

Problems 2 & 3 are unlikely to show on scanning.
I see 5 or 6 cases like yours every week (not the same people!) Most people respond to what I have suggested. The difference with your case is that you have not been treated correctly, in my opinion from thousands of kilometres away.
I cannot treat you, therefore I can only provide the opinion and suggest the treatment likely to assist. Finding a therapist to do exactly what I do is impossible, just as I cannot treat like other therapists. We all have our techniques.
What I do is not gentle. Gentle does not seem to work for these cases.
Once again, I hope this helps.
Note: I may not be able to respond quickly over the next few days as my Father is in hospital (coronary care unit).
MrPhysio+