h2m, thanks for your kind words. I hope you have success and you have discovered what you were missing. I wish I had all the answers--I know I don't....It is unfortunate to read Hunter's sitch (sorry for the 3rd person H-fox!) because it sounds like it is several years deep now. That's a heck of a lot of time, which always seems to be proportional to the amount of effort required.
I have read (thanks Dr. Phil) that one of the 'bad spirits' that people sometimes bring into a relationship is the insecurity bug, the one that needs constant reassurance. If this describes your W, Hunter, then the effort and patience required of you will be great indeed, as her fear of an affair is only a locus for her insecurity, something she attached onto several years ago and uses to channel reassurances to make her feel good about herself. This is not something she will likely give up easily and I'm no psychologist or anything like that, so I don't have any experience to suggest how to overcome this. Maybe a higher dose of what I mentioned above.
Then again, it may mean just going back to the simple, tried and true. Learn her love languages (see 5 love languages, by Dr. (Gary ?) Chapman)...push her positive buttons (remember that if we can know a few buttons we can push that totally lights her up like a firecracker and has you eating from a dog dish for a week, you can certainly learn buttons to push that trigger all the good stuff too!) over and over again.
I think once you really dig deep and find out for certain what love language she speaks, and you start speaking it, I know from experience that the light switch literally gets flipped and it can sometimes turn things around in a matter of days or weeks. She will feel so loved by you, UNCONDITIONALLY (so important here), that she will be so wrapped up in that feeling that she won't have any room for that old INsecurity blanket.
All I can suggest is to give it a try. Test and monitor. Stop doing things that don't work. We are creatures of habit, the only beings in nature that claim to have rational consciousness, yet the only beings who get into habits that don't work. Even rats can learn to modify behavior to achieve the expected results...we should be able to do the same!