Is this it?

[Memom]

Last night DH left. We had argued about something and nothing then he broke my heart, he said I was a poor mother and he felt sorry for my abusive ex husband.
We have a SEN child together and I have adult children. He has been distant since little one was born 6 years ago. I'm lost. The hate in his voice. He is a very mild, calm man. I just don't know what to do. I'm alone again. Little one is okay for now, I've said he was called into work. I'm rambling, sorry.
I could never trust him after what he said, too much to forget let alone forgive. What now? I'm tired, scared and totally drained.

He's said some awful things OP and you know you can't forgive or forget them.
For now take it 1 hour at a time.
Try to eat or at least keep your sugar levels up and keep yourself hydrated.
Do you have family and friends you can talk to?
You need some real life support right now so please talk to people.
When you are ready, start to look at what you need to do to keep you and your DC safe with a roof over their heads.
If you are really struggling then a trip to the GP may be the best thing.

I think that it only takes someone to say or do one unforgivable thing to totally destroy a relationship. I quite understand why you cannot forgive the things he said to you.

However, one thing that really stands out is where you state "He is a very mild, calm man". If this is really true then I would be very concerned at him losing it and saying such a thing.

You say you argued over something and nothing so his response seems OTT. I don't mean to be offensive but, if he is so mild and you consider the argument so trivial, could it be that you lack self-awareness and his blow up is a result of constant issues (something and nothing to you) and this was the straw that broke the camel's back?

Or could he be ill?

What would make a mild, calm man say such things? Do you think there is something more to this?

I thought the same as CoolJulie. The episode and the description of the DH don’t add up unless there is a lot of context being left out. Based on the very little information provided he is critical of you as a mother and a partner. Whether that is reasonable or not who knows.

But one way or another he seems to be done with things as they are.

He has turned up this evening for his tea as if nothing has happened. He spent a lovely night in a nice hotel. His reason for yesterday was he had just had enough and had spent some time considering his life and the choices he had made.

I'm more confused than ever now.

I'd say you need a quiet night to evaluate the relationship too.