General Skywalker grants: Momentum (If this character moved this turn, he gets +4 Attack and +10 Damage against adjacent enemies)

Yoda's Galloping Attack reads: (As this character moves, he can attack each adjacent enemy, +4 attack; this turn. This character cannot attack any enemy twice and cannot move directly back into a space he left)

How I am interpreting this is that all of Yoda's moves are getting a +8 Attack and +10 Damage a swing since he is fulfilling the prerequisites of momentum.

But since Anakin states that the piece must end their move to get it, does it only apply to the last galloping attack and the following single attack, totaling 60 Damage on a piece?

I had this same problem when I was trying to give Darth Zannah Momentum. Ultimately, I just decided she was a crappy piece and went with Mace Windu.

And maybe this is beyond the scope of your original question, I'll offer you a crucial-and-yet-often-forgotten tip about using Yoda on Kybuck: while it may be tempting to tow Yoda out and use him to Gallop right away, that will often be suicide because everyone else will pile on him and eat him for supper. Instead, tow him to a safe-and-yet-forward position with R2, and then activate another piece (maybe run a Rodian Brute up to be adjacent to R2). Then, when it's your turn again, gallop him out with your first activation. Then use Captain Panaka's CE to swap him back to safety (ideally adjacent to R2D2 again), where a Rodian Brute used to be. Now your opponent has taken 20dmg many of its pieces and up to 60 dmg on other pieces, and all he can do in retaliation is kill a meaningless fodder piece. Now rinse and repeat. Most people want to gallop right away, and that is almost always a bad idea.

Skybuck is one of my favorite squads, ever. It has lost a lot of effectiveness (comparatively) over the last year or two, but it's still fun to use.