Ditto on the confusing $4 straddle, but it doesn't really matter, I'll just assume the game is 1-2 and it was actually a $4 straddle.
Preflop is either a fold (which, unless you love playing for stacks with A8o, is the correct choice), or a much bigger raise. At least $25, $30-35 is better, you at least have some hope of getting heads up. At $18, you are ALWAYS going to get a bunch of callers. Sure enough, you did.
Between preflop (you + 3 callers) and the flop (you, mp1, and lp1) you lost a player...was it 3 or 4 ways? Doesn't really matter, because when mp1 leads for $50 the worst he ever has is the A
. More likely a set or two pair that is scared to see another heart. And he's never ever folding to your shove. He's getting 2.5:1 on a call (that's close, your description is confusing). Even if he should fold the naked A
, he's never going to at that price, and that's a small part of his range anyway. Most of it has you drawing stone dead, and will call.
Edit: I had a brainfart and forgot there was another player already all in. Even less likely you're ever good here.
Brutal honesty, this is really butchered. If the results here are that he called off with a flush draw and missed, tip the dealer and don't try it again.