If it's interfering with your relationship, you have to let him know that he wanted to end this, and he can't just talk to you like everything is normal and no big deal. You are pretty much in purgatory, not together but everything else says otherwise. This is the part where the lonliness kicks in and he's probably getting desparate, hence the texts. This will not only not help him deal with his feelings, but pulling you into his baggage too.
You have to remind him that you need space from this too. A good amount of time, not just a day or a week. Get yourself back into doing things that make you happy. I'm not saying kick him to the curb and start dating somebody else immediately. Unless you want to do that. But nothing is going to be solved out of his desparation and lonliness.
I'm still have feelings for my ex, and I just went on a date with a girl last night. She asked me questions about my ex strangely and by my tone she could tell how I felt. It's concerning to me that it might interfere with my appreciation of the new girl so I'm kind of caught in limbo now. I guess I'm saying this because this should be the time that you figure out feelings, not when you are knee deep with another person that really cares about you. What brought these feelings back about his ex? Did she start talking to him again? Has this been a pattern for a while? There must have been some signs to read.
I guess this won't really help you get your mind off it, but don't let him flip flop on the decision. Remind him the next time you talk that this is what he wanted and he can't have you as a cushion the whole time because it isn't fair to you. He'll more than likely come running back. That's when you make sure it's for the right reasons (he cares about you) and not because he's lonely now.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.