My husband cheated and now I want a trial separation?

I think he needs to prove himself to you. You said that you've found him in a few indiscretions so this wasn't the first time he screwed up. I don't often recommend separations but I think you could both benefit from one. It is great that he's a good dad but there is nothing that should prevent him from being a good dad if the marriage doesn't last. I don't think he sounds like a good bet.