I was going to start with one thought about honesty, then another thought came up.
A woman with whom you have a rocky history, who wanted a D, left the M, still has issues with the children and you pursue like mad, justifying ever seemingly irrational behavior, and then meet another (cute, personable by your own admission) woman, who seems interested in you (though is likely deranged), where there is no negative history and you are worrying about X finding out, because you do not want to hurt her?
Sorry, I'm going to say it. AAARRRRRGGGGGHHHH!
Here is a crazy idea, in our new state of self-awareness, and knowledge and R understanding.
Since there is nothing to lose, tell her the truth, tell her you may be interested, but you still have strong feelings for your X. If she is still interested, great, if not, there was not too much emotional damage wrought.
