Hey Bright, I really don't think that him joining a dating site has anything to do with your emails back and forth. Please don't take this wrong because I would never hurt your feelings but I think it all has to do with the fact that maybe like my H he is just an idiot. He did it because HE wanted to. Don't you dare carry any guilt over him being selfish and all wrapped up in HIM.
I won't comment on snooping. I know it is stupid and it does hurt me but since my H lies all the times i have had to do some myself and found out some stuff I needed. Bad Limbo I know.