The levator scap is only really under any load if the scapula is rotating outwards and upwards (to help rotate it back down/oppose the excessive movement). This is only really going to be an issue with 'loads' (rather than movements) above the horizontal which is perhaps not so common in your vocation.

I would keep looking to the nerve as a cause of the irritation to the muscle. Of course GH stability is or paramount importance but this might not be causing your issue. It adds weight to my initial thoughts that you have a history CT junction issues as tightness or restricted movements in the lower neck will cause excessive movements and protration of the neck higher up. In this case taping to inhibit the traps would help (perhaps try some Kinetic taping during Salsa training). Again that points to the neck and vertebral positions as possible suspects

Let us know how you get on. Look at the basic concepts and try not to over analyze the situation with the PT.