My thought it you sound like you have a great grasp of it, and are on the right track. I agree with almost everything you said.
Is this OM married? Have you considered a full-circle exposure as part of your plan?
How old are your children again?
The only thing I disagree -- sort of -- is on the account block thing. I might also DO it, but I would TELL her that I'm doing it, and why -- listing the same reason you gave above. I did this with my wife's cell phone, and a few other affair-related things, and told her "I will not pay to enable you to have an affair." I think it comes across as MUCH stronger, rather than sneakily using technology to block her access, which she will only view as childish.
If you want, I can dig up a copy of my "Finances" e-mail that I sent to my wife, and share it with you. It included not paying for her tummy tuck, cellphone, make-up, lingerie -- anything that she was using to facilitate her affair and to make her more attractive to someone other than her husband.
