Seriously, fuck the Stray Demon boss. I cant even connect with him before im dead. Should I come back later seeing as hes an optional boss?
Stray Demon is both the hardest and easiest boss in the game IMO, up there with my favorites too.
He's purely about learning his attack patterns and kicking his ass legitimately. It takes about 5-10 tries to get it down but once you do, he's easy. Watching a vid will help but it won't win the fight for you, you really have to get in there and just learn it through trial and error.
Stray Demon is now one of the first bosses I take out in the game, usually at around level 15-20 so your level definitely isn't an issue.