With an A being over, there will be several mini-bombs as you make new discoveries and new revelations come forth from W (or around the condo). As you say, not pleasant at all. The A had been going on for 2 years and there will be some things that were not entirely purged during the big CLEAN OUT phase conducted by W at the condo.
I am sorry that you've had to see the XOM's t-shirt. That would have made me blow a fuse because it would be reminder that they were intimate and not with me. A reminder that someone touched my spouse's body, someone who traipsed around the house, etc. I would have burned down the whole house with all of the furniture they've shared. In fact, I told myself before that if Ms. Wonka and I ever reconciled, then EVERYTHING would go except for pre-OW stuff. Seriously, I could not possibly stomach looking at the stuff they brought or shared together. No way!
Your frustration and anger with the knowledge that you had a SSM for 4.5 years....yet W went outside of the marriage to have sex with someone who's not her husband. That would have burned me. It did anyway. Made me feel inadequate and made me feel like such a loser.
It takes time and space for you to work through those feelings. All of that is complicated by the fact that W has STD and you two are the victims of that. Incredibly unfair...for sure!
Yeah, at some point down the road, I think it is important that you discuss those feelings with W. Not now. Several months when W is more centered and emotionally stronger along her own path. Right now would be a very bad time to broach this subject.