You know I'm not going to judge you for your part in this by any means. As you know, I unknowingly (at first) went into my relationship with my now husband while he was with someone else, and then he ended up marrying her 6 months after we started dating. It was a nightmare but today, I wouldn't say I wish I hadn't gotten involved with him.
There are situations where things can work out, but no, I wouldn't intentionally get involved with a married man unless his wife is cool with it! Being poly, the rules are definitely a bit different.
I wish you healing, my friend. xoxo