Hi Aria - love the chosen name
I applaud you for your level headed approach to this. You seem more than reasonable given the fact you are unsure about this for yourself and what it might mean long term. Kudos to you girl !
I think he needs a wake-up call. We can only go from your words and the one side but you seem the type to be reasonable and accurate so.......
You are undoubtedly familiar with NRE. If not, read up on it because his behavior is somewhat typical for poly newbies in that phase. That is NOT an excuse however - only a partial explanation. He needs to be called to the carpet on it and accept responsibility - AND learn !
The unprotected sex with a literal stranger is a bad pattern. How bad depends on a variety of things such as the location & background of you all etc. I know there are some who would consider it the ultimate sin/risk but in reality I feel that has to get tempered by the lifestyles and history of all involved. I'm not one to fear that 98% of the population is carrying AIDS etc but for some people that IS a reality so it's case variant. In any case it's a bad practice to adopt as a rule.
The not checking in with you, especially under the circumstances, is just plain immature and irresponsible. I'm sorry. For me, and most people I know or have met, that would only be common courtesy for someone you care about. We even call our friends or family to let them know we've arrived at a destination, or that we are leaving and on our way home etc just to eliminate worry. With a mate and children this kind of thing is simply critical. It's NOT some control thing, simply basic consideration.
If you guys are going to embark on a poly lifestyle you both are going to have to open your minds to learning some new expectations and better communication skills. Little things can matter a lot - more than they otherwise might have. In short, it's no longer safe to ASSUME anything ! Everything has to be thought through and talked about to make sure everyone is on the same page. This is part of the new "work" that you hear so many poly people speak of that you might get by without in a mono arrangement. Mono arrangements coast along with a lot of 'assumptions' - not that that is good or desirable either - but it's the way it is. In poly that's a prescription for disaster !
Get talking and pass the 'bad boy - slap slap' message on to him. Strike one !