You need to decide together what is and isnt important.
He may think certain things are really worth battling over, whereas you don't and vice versa so you need to choose your battles together.
How do you say to him about something you don't think is important? I try to make sure enver to ever say anything i front of the kids, or if I'm less than calm and once everything is alright I'll say to DP, 'I think you should've handled X in this way because...' and then explain.
For example, we were talking about something we didnt want the kids to hear the other day, DS came in the room, was told to go out and we'd be out in a minute, 5 minutes later he was back. DP got really annoyed with it, because he'd only just been told to go downstairs and wait. I explained DS was 3, and probably not much more intelligent than a dog wrt time and space, 5 minutes is a long time, probably comparable to an hour, so he was wandering around downstairs being a 3yr old that was bored and thought 'oh, lets go see mummy'.
When I get DP to see things from their POV it is much more beneficial than if I was to criticise him and his techniques. An hour later DS did something that wound me up, and DP just said 'remember what you said about dogs' so both of us are more capable with delaing with things because of that chat.
WRT their father if he is that useless when they grow up they'll realise, I sometimes wish my DC's would realise just how much I do for them, but it's part of being a parent, you don't get thanks or praise, not til they're parents themselves.