If you found really young girl porn, he should be reported to the authorities. There is no excuse. Children are abused specifically to produce this stuff for people like him. If he has child porn, he should be held responsible for it. By protecting him you are also committing a crime.

Furthermore I don't care what "most" pedophiles do. Not a chance my kids would be anywhere near someone with those tendancies if I was aware. I applaud your decision on that one.

Report him to the police and get a divorce.