I like August. It's popular in Scandinavia so I think of a cute little blonde kid

I don't like the nicknames for it, though, so I probably wouldn't choose it unless you are OK w/ him being called Gus or Auggie perhaps occasionally.
Clark is OK. It's my maiden name and we considered using it as a first but ultimately decided it was too nerdy and too Superman for us.
I really dislike the name Anthony and the nn Tony. I just don't like the sound of it. And FWIW, I've known plenty of Anthonys who were not Italian--including 3 Vietnamese Anthonys--so I really don't think of it as an Italian name at all.
Luke is my favorite on your list and the only one I'd actually use myself. I do like the name Luca as well if you're interested in a similar sounding name w/ a bit of a different vibe to it.