One tip for dealing with intrusive thoughts. If you find your mind going back to the same topic over and over again, give that thought or collection of thoughts a file name. Then, when you catch your mind going to that topic, picture a filing cabinet and stop to think to yourself, "I have the [fill in the blank] file out again." If the recurring thoughts are intrusive and not helpful to think about in that particular moment, then picture yourself opening the file cabinet and putting it away for another day. For me my files are things like "Oh, I have the mistress pulling up in my driveway file out again," or "Oh, I have the coming home to half the furniture being gone file out again." Similar to picturing a stop sign it helps to regain some control over what you think about.
Also, it can be helpful to keep an actual written checklist in your pocket for when the 10% doubt occurs. What things does he do to make you feel loved? List those things. Then, when you feel doubt try to recall the most recent time he's done those things you listed. Since you said he is in fact doing the things you need him to help you heal you can sort of talk yourself down from assuming the worst about him.
Hope this helps!
BD: Aug 2012 Separated since May 2013 S born Aug 2013 Aug 2013 H agrees to consider 'baby steps toward working things out' H is/was actively seeing someone?