i disagree with you saying that this line ALWAYS means business at these limits. i play the same limits and i get player call preflop raise/call cbet/ raise on the turn on bluffs pretty often, that's probably because i establish a loose table image at most of the tables i play.
that being said i'm folding lol. it's really tough to put a player on a bluff OOP and you're probably better off taking the safe route if you're stumped (i know that my biggest leak is making a silly read that a player in late position is just jerkin my chain)