[ModusOperandi]

The decision is entirely yours to experience from.
However, if I were to put myself in your shoes, I'd move on and steer clear from this guy for 3 reasons.
[edit: misconception deleted. :P]


1, 2 and 3. Shortly after reestablishing communication with his other ex-girlfriend, he feels it's necessary to ask "me" permission for him to rekindle that specific relationship thus, leaving "me" behind.

Clearly, if this guy cared about me, he would be telling his ex-girlfriend that he's interested in someone else (me). Not the other way around. Forgive my bad analogy but, I'd automatically assume that he thinks of me more as a support crutch to lean on every time he "sprains his leg." A dispensable item to be tossed away once its services are no longer needed.

I wouldn't waste my time.

Of course I'm basing what I'd do solely on the provided information....
Since you're the only one who knows the situation in its entirety, well...I'd think very carefully about this if I were you.