OP I am glad that you are still posting.
I hope you're feeling in a bit less of a whirl and can start to think a bit more clearly.
It's great that he's gone away for a couple of days. Use this time not only to THINK but also to remember YOU. Who YOU are. The ideal you, the mother of your children, the unique person you are who has a duty to herself - as we all do - to work towards being happy, functioning, enjoying life, getting the most out of it.
What kind of future do YOU want?
Finishing this relationship and going it alone - possibly temporarily, possibly permanently - is no doubt a very daunting prospect, and a sad one, when you felt that you had the setup you wanted.
However I think you know that that is far far preferable to living - no, existing - with a relationship which has had the soul ripped out of it.
My personal opinion is that that has DEFINITELY happened. Not just because of the incident, but because of his response. His reaction, confirmed in your last few posts, would absolutely confirm to me that this man isn't a good person.
A good person who had a moment of madness would be DISTRAUGHT. Him: sorry's enough, it's not that bad, you are overreacting.
You aren't overreacting: what he did was violent, frightening, and most of all a HUMILIATING act which showed utter contempt for you. That says more than words ever could. I couldn't IMAGINE the lack of human feeling I'd have to have for someone before I could throw a drink over them. The thought of even having to witness such a thing makes my toes curl with embarrassment and horror. And a drink doesn't have to be much more than 'lukewarm' drinking temperature to burn. He could have burned your face. Easily. There was no safety valve which stopped him, although we all know without having to think about it that if you eg poured drinkable tea over your hand, you'd be yelping in shock at the heat.
A good person who had a moment of madness would absolutely understand how you feel now. It is SIMPLE. It is OBVIOUS. Someone has attacked you. The person supposed to be the one who cares for you has been violent to you. YES you fear it could escalate. YES you lose trust in them. Um, what on earth is there to debate in that?!!
Him: you are 'ridiculous' to think like that.
What does this say? Well, for a start it isn't ridiculous - look at the other stories on here - the evidence says that it's pretty bloody likely that a person who thinks it's ok to attack someone and that he hasn't really crossed a line will in fact continue to become more abusive. It's not even the having done this once, it's the dismissing it. THIS is what should tell you, in red blaring klaxon letters, that THIS ISN'T A GOOD MAN.
A good man could conceivably act violently under great stress, yes.
A good man could NEVER, in the cold light of day, sneer at his shocked partner that it wasn't so bad. That she was being 'ridiculous' to suggest that he might hit her. That she was overreacting.
You say your fear is that you have lost trust in him. I hope you have - it is the sensible and logical way to feel. I do not believe that you would be able to have a happy, relaxed, truly positive future with a man you don't ultimately trust or feel is a good person - living together, having sex together, seeing him parent your children.
You have had this man in your life for 3.5 years. 42 months. That is nothing. If you do nothing else, take a step back and try and get perspective on that - think of other relationships and how life felt when you were inside them and how you moved on successfully. You can most certainly do that. The bigest shame in all this might be that you allow fear to stop you taking positive choices - to want BETTER than someone like this. To want a BETTER life than always feeling crap about the person your partner is.