Much of it sounds pretty familiar.
Have you had any therapy for the scoliosis & posture issues?

I would consider looking into some body workers, expert ones not beginners. Alexander, feldenkrais - lots of styles of it.

There are a lot of videos online about posture, chiropractic, stretching, bodywork - Google videos or you tube are great for learning about some of this stuff.
Also some vids will show if you search thoracic outlet syndrome.

If your hand is white even with arm down - I'd get that looked at from a circulation stand point at least.
It might save you some time to track down a good dr that is open to considering TOS at least as many will pooh pooh or totally ignore the idea - or they just plain don't know beans about it.

Or even seek out an advanced PT or expert chiropractor for evaluation purposes. Then ask for a MD referral or take that info to a MD.
Sometimes PT places have a good idea of what dr is good for certain conditions...

What kind of work do you do?
many accidents/whiplash/ sport injuries etc?

One thing is try to keep aware of your posture and gently work to bring those shoulders down and relaxation techniques will be helpful also.

If you haven't found the useful stickys threads yet be sure to look thru those for much more detail than I can cover.
look for the green icon w/ arrow above the main thread list.

The constant tight muscles might be spasms and a good PT or some chiros will do ultra sound , heat, IF stim to get those muscles to release/relax before attempting any other type of treatment. You may have some trigger points also & those will need to be addressed early on.