Why not just be his friend and accept the relationship where it is rather than suggest divorce? I understand you want more, but why not just take it for what it is?

I wouldn't tell him I was dating (be mysterious!!!). I'd become his best friend, try to be the one person in the world he feels he can talk with easiest, the person who smiles at him all the time, bolsters his ego and makes him feel like a man. Do this for awhile... That's the first step...

Then the next step... Rather then say you're going to date (which will just make him angry, sound like a threat, and help him leave the marriage for someone who is more interested in him). I'd act like I'm happy, healing, developing a great life in spite of things (act it, think it, and it will happen!). When I'm leaving after doing the accounting, or dropping off paperwork, I'd look super HOT, keep looking at my watch like I had to be somewhere, maybe reapply some red sexy lipstick, check on my nails, and then smile and say, "Ooooh gotta run!" I might wink at him and have a slightly guilty look, even give him a hug! -- and then run off to Barnes and Noble for Starbucks and to sit in the ailes to read books!!!! While all the while he's wondering... Where did she go??? Why did she look so nice??? Who could she be seeing???

And if he asks later... "Hey where did you go the other day?" I'd just give him a sly smile and say.... "Oh, just out," and then change the subject and focus on him.

There is no arriving, ever. It is all a continual becoming.