I think a defense of 5 would be good here if you are going for Captain America power level. It's tough to judge how One Shield Defense and Ruthless Counterstrike would work together so you may drop it during testing if he's coming across as too powerful.
I really like the SA here, it's innovative.
For the class I'm really not sure. They all sound thematic for him after a quick wiki read so it's really just a choice as to what synergy we do/don't want him to have.