How to help an angry/stressed partner

Hi, 

I'm suffering from PND & on Sertraline 200mg. I'm worried about my husband's behaviour, he won't accept help & I don't know what to do..

He is stressed a lot of the time, and puts it down to work but it's happening just as much when he's not working, he is quick to anger & raise his voice and can be too rough with our toddler (like grabbing him by the arm hard to stop him doing something or throwing him down too forcefully onto the sofa where his calm down area is). He often goes around in a clearly bad mood which in turn brings my mood down & means he has no patience with our son (2.5yo). 

He has been like this for a while, probably since around the time we had our son in 2018, but now my son is a toddler and very challenging my husbands anger & bad moods are becoming more obvious and I don't like the way he treats our son. It's also a trigger for me and every time I hear him shouting or getting angry it makes my tummy drop & flip & I often end up in tears myself. 

We've talked about it several times & I've asked him to reach out to his GP or self refer himself for talking therapies but he refuses. He thinks he can handle it himself, do meditations, exercises and gratitude lists etc but then makes excuses that there's never the time to do them etc. We made a plan of how we are going to react to challenging behaviours from our son using the gentle parenting method & I stuck it up on the wall but he just doesn't follow it. We have been trying to both talk about our mental health each day and how our days are going etc but it's not been making any difference to his behaviour. I'm really fed up of it and having to tell him to be more gentle/careful/calm etc with our son, and we have a 5 month little girl and I just look at her thinking is he going to shout like this and be angry with her too when she gets older and it just breaks my heart. He's not like this all the time, some of the time he can be lighthearted & fun (which is what he was mostly like before we had children), but it's the minority of the time now unfortunately. He does help with our children and will sling our daughter while he’s working from home or come and help me if I’m struggling with them. He does a lot for our family & works hard. When we have talked about it he is ashamed of his behaviour and talks about ways of changing things (like talking daily about our mental health) but won’t seek further help (even though I’ve explained why it could be helpful it’s like he doesn’t think it would be). I really don’t want to leave him, I do love him, he’s my best friend, and I don’t want to break our family up, but I can’t let him continue behaving like this and at a loss what to do! I’ve thought about taking a break and going to my mums, but it’s difficult as our close family & friends are over 3 hours away, and I have a difficult relationship with my mum so worried it could make my mental health worse and I think I would also feel very lonely without him & without his help for our little ones. 

I'm sorry for the super long post! Just really struggling with my own mental health at the moment, I feel like my life is falling apart and I am scared of what our future will be and what my future would be if I did leave him. 

Any advice would be amazing 🙏