It sounds like you are still harboring a lot of hurt feelings from the relationship that you had with this man.  First, you mention several times the pain he put you through.  Second, you seem to be very angry about him asking you if you had sex with anyone else.  It doesn't seem too unreasonable that he asked you. 

He was projecting his untrustworthiness.

You were separated at the time and there is no reason why you couldn't have sex with someone else, right? Are you perhaps more angry about the past pain than about the question?

The critical questions now are:

1. Has he really changed?  You want to be absolutely sure that you can trust him if you are going to move in with him.  If there is any doubt in your mind, postpone the reunion. 
2. Are you going to be able to forgive him?  If he's changed, you need to give him a fresh start or you're both going to be miserable. 

He probably won't apologize every time you feel it's appropriate - no matter how much pain he's put you through in the past.   If you can't forgive him - and I wouldn't blame you if you can't - move on and stop trying to make it work.

Finally, if he does have a sexually transmitted disease, you need to protect yourself from it.  Condoms are the easiest way and abstinence is the most foolproof way.  Don't mess around with disease or you'll have it for the rest of your life.