do to the cards wording i was wondering if there is a way to break Tomax

The card text says: Once per round, after you discard and Elite Upgrade card, flip that card faceup

so what if you have Tomax with Crackshot (when attacking you may discard) and cluster missiles (attacks twice)

so Tomax attacks for the first time this round and uses crackshot, his ability giving it back to him (as it satisfies "after you discard an ept"), then on the second attack he uses crackshot again on the second attack, his ability triggers only once per round so he doesn't get it back. and next time he attack he cannot discard the ept and therefor cannot get it back

am i correct?

Correct. Tomax can only use his EPT once per round if he wants to keep it, but can discard it for good to use it twice (remembering once per opportunity, so no doublecrack to cancel 2 evades on the same attack)

"Perform This Attack Twice" is considered two opportunities for such things.

Yes. Tomax can either use Crack Shot once on one attack and get it back, or once on each of two attacks from Cluster Missiles and lose it for good.