Hi Cassi,
So the bank allowed you to change your payment terms i.e. go interest only without your ex's signature on the forms? Interesting.
I suggest you contact the bank and clarify the position of the title deeds at present. It sounds like currently the deeds are fully in your name, your ex has been removed from them, but his name is still on the mortgage. But you need them to clarify that.
If that is the case, then I guess eventually when you have paid off the mortgage, the house will belong to you alone - but ask the bank to confirm that also. There is probably a point at which they will allow his name to come off for example when the house has built up some equity or worth, maybe you don't have to wait til the mortgage is fully paid off?