Thank you, Redpepper, for taking the time to read my story and provide your insight. After re-reading my post above, I have probably included a bunch of irrelevant material, and may have left relevant stuff out. However, I guess I'll address that as it comes up.
I am going to take your advice...at the very least, I don't want to add any more destabilizing effect on J and R's relationship. I don't know if they will be able to save it, but I don't want to contribute to breaking it faster. I'm going to be seeing J on monday for another ski trip (along with one of his co-workers, who as far as I know is not aware of any of this stuff) so assuming there is a chance to talk to him, I plan to try to discuss much of this stuff with him, and get his take on how to approach it. I really want to try to work out a way with him to get D and R fully in the loop on who knows what about J and R's potential divorce...I'm somewhat uncomfortable continuing keeping the truth from them.
Again, thank you for your continued advice!