No nits, but when Wesley said, "Well, zombie it is then." something about his delivery just reminded me of John Cleese as Basil Fawlty.
("Well, zombie it is then. Whatever you do don't mention the brain eating. I did once or twice, but I think I got away with it.)

The zombie boyfriend was quite an amusing idea and done well but in the Buffy episode Dead Man's Party weren't zombies essentially mindless, lacking any emotions or personality traits? Whilst it is entirely possible that a different form of magic or other mystical energy could produce different results there is no explanation given in the episode for this apparent lapse in continuity.

Actually he was like the "zombies" in The Zeppo (Buffy, season 3), which were so life-like (other than the obvious signs of putrification during the time between their deaths and their "resurrections" that Xander did not realize that Jack wasn't alive. If they were going to explain the differences away, then would have been the time. Unless they just assume we would expect that different resurrection techniques would have different results.

Different resurrection techniques have different results. Dawn resurrected Joyce as a zombie, but luckily we didn't have to experience the horrors of that change.

Speculation (and possible spoiler):

I think Billy is Connor.