Here is something to consider for perspective: For the things like being late, ask yourself, if he were late getting back from the grocery store what would your emotional reaction be? Personally, it irks me when people are late and fail to inform me of it - even if it is just what time I can expect the person to return from the grocery store. If you feel as I do about such an issue then use that as a baseline, and any other emotions you piled on top of it relating to your guys behavior is probably the polyamory experience. You don't need to feel any more disrespected for his failure to check in than you would under ordinary circumstances - and given the fascination with the newness of everything, it might be somewhat understandable.
In such a case - if it were true - I would probably point out to him that you would be irked for failing to at least let you know he was going to be late regardless of where he was, and then ask him how he would feel if your positions were reversed. A lot of successful relationships - polyamorous or not - are based on good communication, and mutual understanding that comes from being able to put yourself in the other person's shoes.
Now, Marcus does have a point that perhaps the best way to deal with it would be not to make rules that set everybody up for failure. The thing of it is, if you chuck the check in at a certain time rule (or come home in this case), then your guy needs to be willing to live by it when you are the one out on a date. If he's not, then he needs to act like an adult and abide by it. (Seriously, it is the new girl's responsibility to make sure he meets his agreed upon responsibilities with you?)