After two months my shoulder weakness is greatly improved.
The lateral winging is mostly gone (or is minor and symmetric on both sides )
So I suppose my trapezius has recovered from whatever the nerve damage was.
Still have my usual medial winging though. But I feel this is simply due to a weak serratus anterior muscle rather than a LTN nerve problem.
Second EMG came back notmal.

I can feel my serratus anterior working if I do scap push ups, but I cannot figure out a way to do an isolated activation of it. Scap push ups are flaring up TOS symptoms in my arms and give me wrist pain so they probably do more harm than good...
Push ups from a wall don't seem to do much: I cannot feel that serratus anterior is even working.
Are there any good safe serratus exercises?