]Don't you trust his judgement? Do you think he would have barrier free sex with someone who he isn't sure about? If so, that is your issue. I'd forget the poly thing altogether and work on establishing trust and respect.
I already said what she should do if her partner isn't trustworthy. As for him lying about using condoms, it might have been different if she gave him a way to have PIV sex. Even if it meant waiting a year. If you want people to be honest with you, you have to create an environment where they feel they can be.
As for should, we are in a forum, giving advice, we are all telling people what we think they should do. Regardless of how we phrase it.
Again, if Dana wants to save her marriage, she should look at ways to start having sex with her husband again.