You didn't mention your age, but reading this from my age (29) and being a male, i can say that your conclusions don't match mine. All that i see is a guy trying to set someone up for the mistress/safety net position. Even if the choice of words is pretty nice, the facts remain the same:
- he is with that girl and will continue to be with her
- he wants to have sex with you while continuing his relationship with her
- that's about it
Your conclusion that he "tries to re-live your relationship with that other girl" is severely faulted if you ask me. All you got are his words and that's not a solid base in my opinion. Also, your second conclusion is far more faulted ("he loves you") - if he did love you, in the normal way that 2 people should love each other in order to have a happy relationship, why does your post contain so much "don't want to be alone / coming back with my tail between my legs only to go out again when i have the chance" go back and forth behavior?
You might find my viewpoint overly simplistic, but in most cases, we either try to fill the blanks with faulted assumptions that suit our desires, or get out attention distracted from the obvious by some nice words. Case in point, to me, your chances at a "normal" relationship with this guy got down to zero right about when the "suddenly" and "started seeing another girl" got together. That's not a coincidence, he had a target, pushed you aside, got kicked, came back to a safe place and went out again when a new opportunity presented itself. Sure, you still have chances at a "being the fifth wheel" relationship type with this guy as, heck, he pretty much spelled it out loud to you, but if you're engaging this thinking "I will change him" be prepared for some major disappointments up ahead.