Aletheia's

I didn't like that they had to fight, but I was glad that we could understand where they were coming from.
Exactly.

I do think that withdrawal instead of anger seems like it could be a legit reaction
Yes, this could be plausible. It's understandable that he's just fed up, longing for peace at last, and anyway he must feel quite lost. I'd love to see something like this, and with more complexity, maybe in stages: first withdrawn and subdued, and this building up to outburst of pain, when cornered. But this would demand exactly what was missing there, that is the plot spun around him as one of protagonists rather than the plot pawn he was. So:
it would have been good to see more of him as more than something to move everyone else's plot along.
This.

I wonder if he might be back in the Black Panther movie, though, since he's in Wakanda.
Huh, I didn't think about it, indeed. Perhaps I have a reason to see the Black Panther movie after all, or at least to keep watch on it.

Someone needs to fix his arm!
Tony, of course! :> (Shut up, Tony, it's only fair. ^^) With a slab of vibranium courtesy of T'Challa, who I think still feels a bit guilty about his mistake on Bucky, too.

it seems super creepy to me to get involved with the niece of the woman you loved! Right after her funeral, too!
Yikes, you may have a point... (Though I'm pretty sure no one would approve more than Peggy herself. XP)

I liked your metal arm justifications! Usually I just assume rule of cool, haha.
I'm glad it works. :) For me it usually is "Yeah, cool and all that... but still, why???" And anyway as I said, reasoning for fun! :)