Engine Vibration at highway rpm/speed

I just went through the same struggle and tried all the same stuff as you.

I solved it going to a different driveshaft shop #2 and the guy mentioned I had some cheap U joints from Shop #1. He said even tho they were new they could be a problem. He put in some spicer joints, rebalanced it and boom no more vibration. Might be worth a shot as its not too expensive.