Push or Fold?

[buhler26]

We are down to heads-up in a home game single table tourney.
I have the button, with 6/12 blinds. After the blinds I have76 in chips, with my opponent having about 250.
My opponent is a pretty bad player. He has shown several times where he has bluffed with nothing and also called down with nothing. It is pretty late at night, and I think he has mentioned he is anxious to end it.

I have 4 [img]/images/graemlins/diamond.gif[/img]7 [img]/images/graemlins/club.gif[/img]. I call big blind, he checks.

Flop is 3 [img]/images/graemlins/spade.gif[/img]4 [img]/images/graemlins/spade.gif[/img]5 [img]/images/graemlins/spade.gif[/img]. He bets out 30.
I was fairly confident he wouldn't bet out that big if he had a made hand. I put him on overcards, possible with a flush or straight draw. All that considered, is my hand still too weak to push here?