Me (35M) just caught wife (35F) cheating while I was deployed through messages after stepson showed me

While I was deployed my wife was messaging another guy that has very heavy implications of them being physically involved and also her not shutting down any advances from this guy. Towards the end of the conversation I see a message where it says that she loves him. Shortly after this she sent the guy a message that they should only speak through instagram due to her phone not showing she has messages all of the time, this was about a week and a half before i came back home from deployment. The guy was also a soldier at the same base as I, but I do not know him. My stepson said he needed to talked to me and showed me messages that were linked to her Macbook that he had just discovered while he was at school. He is a wreck right now and is avoiding his mother as much as possible. I took pictures of the whole conversation that was available on the Macbook, but cell phone records show them talking on the phone prior to this timeframe. She has been super defensive of her phone since ive returned from deployment when before she always harped on being transparent and also does not share any bank statement info of hers with me when trying to set budgets for the family expense and future. This is strange because I pay all the bills from food, electricity, rent, gas, internet, car notes, car insurance, etc. There are three step children involved and she has no money or job. I will print out the copies of the messages this week. I have not told her I know any of this information. What else should i do besides getting a lawyer and printing out their text history?

Update: I am waiting until Monday for consultation of a lawyer and to talk to my commanding officer. I have the Soldiers name and also their address that he lives at on post. I have not told my wife anything yet. I told her I'm sick so she isn't questioning my down mood at the moment.

Update: she found out my stepson showed me and is blaming him for everything.

Update: considering only petitioning citizenship for stepson since the wife and one of the three children are undocumented. Also considering transferring GI Bill to teenage stepson that provides BAH and opportunity of college. More to follow.

Update: went out with a friend for dinner and a beer. Staying at a hotel for the night. She has not tried to contact me since i went out for the night. No more word from stepson. I expect more hostility tomorrow from lack of communication. Plan to pack up clothes and essential items to move out if necessary. I really want to avoid any domestic dispute.