he has his cake, and is eating it, too.
You were correct on your first assumption. Of course he is playing both sides of the fence. Smart girls do what you just did: investigate, learn the truth, don't hide your head in the sand. Dump this guy on his ass. I'm a guy, I know what guys do. When we behave in this manner you dump our asses on the curb, hold your head up high, and walk right out the door. That's what SMART, CONFIDENT, TOGETHER WOMEN DO. That's you I'm talking about so follow the McCainster's advice.
I tell women all the time to dump guys because there's a lot of bad apples out there. Trust me...75% of all guys aren't worth having! You've got to manage your emotions, don't give all of yourself. I know, I know it's a difficult skill to master, but it provides clear thinking when choosing sweethearts. You want a clear head, don't you? Sure. Emotions lead women astray and they will get taken advantage of. He likes the other woman, so what? For whatever reason you now know what needs to be done. Will you do what needs to be done or waste another five months with this guy? Well?