Hey everyone sorry I'm new to this whole NM thing. I'm in situation though and could use some advice on how to behave going past this bomb that has exploded. Sorry for the length. TLDR at the end

Last year a couple (hetero) who my partner (hetero) have known for years asked us to join them in bed. This is most of the members in this quads first time experimenting with this but so far we have had really good communication and have managed to work through our emotions and have found enjoyment in it. The problem now is one of the other members in the other relationship has committed infidelity and was discovered last night. My partner is close friends with the girl who committed the act and has a great deal of understanding what she is going through and what has led to this moment, while I've developed a close friendship with the guy and thus am currently being there for him but not vocalizing any opinions. They are currently going to try and work it out. The thing I need advice on is going forward how to handle the relationship mainly is concerning navigating our relationship with the other couple. I know a pause is in order with physical intimacy but how should I navigate being a shoulder to cry on for the guy who is now facing the decision of ending a 7 year relationship. I can't expect my partner to not be a friend to the girl even though he disapproves of the infraction and I don't want to leave a friend alone with no one to talk to.

TLDR: I have been in a NM relationship with a couple but now the other couple is experiencing infidelity where the person who commited the infraction is best friends with my partner. I have become friends with the "wronged" member of the relationship but don't know the best way to be there for him without rocking the boat even more.