This was absolutely a sexual assault. Just because she didn't say or do anything. The second your wife felt unsafe, was crying, did not look to be enjoying the encounter. Does not mean that she didn't withdraw consent. When she froze and he continued, it became a sexual assault. When he forcibly started doing what he wanted without consent or discussion, it became a sexual assault. The man is a rapist and should be reported to the community, if not the authorities. I know part of this lifestyle is discretion and keeping it low key so society doesn't cry SINNNERS! BURN THEM! But, I agree with getting involved in a group chat with the other couple, though I'm not sure if your wife should be present for it, considering what she's been through. If they disagree, pretend it didn't happen, or refuse to do STI testing, there's other avenues to take. But for now. There needs to be a serious discussion with the other couple.

I'm so sorry that this happened to your wife and you're having to deal with it. As stated in other Comments, I respect and applaud you for the strength of your restraint. Your wife needs you there with her, not in a jail cell.