I do think you have to talk to him, and you have to sort out his relationship with your DS.
I don't know if pre warning him of a chat is a good idea - I suppose it depends on you two. If it were me then I would just try and bring it up one night when the DC are in bed and you are sitting watching TV or something like that.
Maybe write down what you want to talk about first, like a bullet point memo or something, so you are clear about what you want to say. (But don't sit there with the list, its just so you can have a clear mind).
Also perhaps have a look at relate or some other counseling, and have an idea about that, then you could suggest he/both of you spreak to someone. It sounds like he has some 'issues', with the anger and from his own childhood.
If he takes it badly, and flies off the handle, refuses to talk etc then make it clear you are unhappy/worried to the point of leaving and how important it is that you both communicate and try and put things right. If there is no communication then you have a clear answer.
I would say comparing him to other fathers and what they do with their DC may be unfair. I would focus more on making sure he is treating DD and DS the same. Some people are great hands on fathers and some are not, and even if you split it wouldn't mean he would suddenly put lots of effort in, he may just do the same as he does now.
Its always difficult to comment on other peoples lives though, so I would say you have to trust your gut instinct. If you (and your Dc) are unhappy then don't be affraid to seperate, there are many many families out there going through this every day, and provided your DC are loved and supported then they will be ok. Equally if you can improve your familiy's internal relationships and make everyone happy, then that can only be a good thing.
First thing to do is to open up the lines of communication witrh DP.