IMO. From the outside looking in, he sounds like he is manipulating the two of you (the ex and you) to get what he wants. It doesn't sound like he is willing to be in a 100% committed relationship with anyone at this point.
Aside from the birds-eye view, trust CAN come back. It takes work from both parties. It takes time, but emotional wounds will heal. If you truly love him, see him for who he is. If he proves he is trustworthy, than the good will out way the bad. You too have to work on your trust issues. Why did you have this mistrust in the first place? Why do you feel it to be necessary for you to know what him and the ex speak of in their conversations? Discover where these feeling are coming from and take a look to see if they are ligament feelings of a mistrusting issue, or perhaps an insecurity. Also, the ex will always be in the picture and will most likely always cause drama. Make sure you have your boundaries and are taking care of YOU first.