Youi have 9 flush draw outs.
You also have the non diamond 5s and 10's for 2 more outs, = 4.
you also have 3 more 6's and 7's but you'll probably need 3 of them to win, because i think he's got a set.
so, without the 6and 7's you have 13 outs in 47 cards = about 1:3.5 With just one opponent, you are getting 1;1 odds on your bets; not good at all.
You must also factor in whether you can stack your opponent if you hit your draw. Generally TAG players fold, and loose ones call.
IMO, this is not a heads up hand. This is a great multiway pot hand, where youir bet is matched by 2 or 3 others.
In your particular hand, the questions become:
"Will he call my push if I hit my hand?
More importantly, "If I hit my hand, is it good?"

I definitely fold this hand after trying to win it with a big flop bet, and i find myself heads up facing a big raise.