Re: Wife joined meetup.com?
Sounds like you need to set some boundaries with your wife and your ex to some extent. You should start off the conversation something like... "I know you aren't thrilled with my ex. I don't want to do anything that makes you uncomfortable but I have to have some contact with her because she is the mother of my son. How do we make this work where I can spend time with my son and his mother without it affecting us?" It would also be good to reaffirm your love for your wife as part of this conversation and to do it proactively instead of after something she doesn't agree with has happened.
There is also the lack of communication with her trips and going out. You guys need to get on the same page as far as what is expected. My wife and I know that if we need to go somewhere in town, we don't need each other's permission, but we still tell each other out of respect - usually before the plans are made. If we have to do something that is more than, say 2 or 4 hours in duration, especially if it is an overnight trip, that is something we definitely discuss before plans are made.
I'm not sure if she just doesn't think that she needs your input before making these decisions or if she thinks its OK to leave you out of the decision making process as revenge for some previous slight, but you have to lay down some ground rules and work out past differences or it will eat your marriage alive. A passive-aggressive spouse can be dangerous to a marriage.