Marriage under strain

My marriage with a man with ASD is currently under significant strain. The diagnosis is recent and I have a lot to learn about supporting him and our family in this light, and about my own self care. We have a 1 year old and 3 year old, and this is a major area of strain as my husband gets very stressed by the chaos involved with 2 very young kids -- I know this is common. I would welcome any coping strategies for getting through weekends. We've been each taking one child and doing things separately as this helps my husband's stress, but we both feel we are growing apart as a result of spending little time together. I guess having a highly structured weekend with some routines might help. He gets very anxious about car journeys with the kids due I think to the unpredictability of whether they will cry/shout/get hungry/ need the loo etc.

We've also been through a prolonged trauma as our youngest was born with a life threatening birth defect, had major surgery and spent a long time in intensive care. She's doing better now, but it has caused extra strain and stress and my husband is suffering hyper vigilance too, which I recognise is really hard for him. He says he doesn't want therapy. He also has a demanding job. Overall his stress levels are such that at home he is in very withdrawn states most of the time, in which he speaks little and seems quite angry. He often attributes these moods to something I've done, but it will be something small (an impatient remark), and this state of mind will last all day. If I look at the bigger picture I'm sure his overall stress is a factor. I would really welcome strategies on how to respond when he is in a withdrawn, angry state. It doesn't seem he wants to be left alone as then he feels I am avoiding him, and finds that hurtful.

He tends not to accept his diagnosis, and he questions the validity of diagnoses/labels in general. I respect that this is a position, but it makes me feel very alone in how to best manage things for the family. Also, it means, for example, that he doesn't want to see a relationship counsellor with ASD experience, which is what I would find helpful.

Sorry for a long post. I'd be really grateful for advice relating to any part of these difficulties. If things remain this hard I'm not sure I can stay in the marriage, but I want to give it my best shot. I do wonder if it will get easier as the children get older -- have others found that?

Thanks.