Cinders is right and if you haven't learned this already, you will learn it quickly. The kids are in the middle no matter what way you slice it. If they confide something in you about their dad and you confront him on it, he will more than likely be upset with your kids and in turn, your kids will be upset with you...vicious cycle! I have had to deal with this kind of thing so many times over the years. You need to choose your battles carefully.
When I was going through some custody stuff with my XH, my H would always say that I just need to keep everything documented. So, keep a journal with all of the details. If a time comes when you need to take him to court, you will need all of that detail.
Now, I talked to my H just a little bit ago and he was talking like a truck driver. Sounds kinda like your H huh! What's up with that?
