Can I say that you obviously have a great relationship if he can behave like this with you. It's like toddlers, he obviously feels loves and supported by you which is what allows him to be able to lash out. It will also be good for him in the long term.
I say this from the angle that my dad dies when I was young. 6. I learnt very quickly that I wasn't allowed to have emotions because it would upset my mum. And I could never go against what she said as she didn't have anyone to support her. It meant that I could never throw a strop as a teenager, missed out on a lot of normal teenage experiences because I knew she wouldn't like it. I was also very aware of death, obviously, so I was worried that if I upset her enough she would die (not a very rational one, but something I'd believed for many years).
So I ended up very closed off and with many emotional problems. I didn't really have a relationship til my mid 20s, as I didn't believe I could be with someone who'd let me be myself. I still find it amazing that I can be 'horrible' to DP (ie tell him I don't agree with something) and he doesn't storm off in floods of tears.
I'm not sure any of this waffle is helpful, but please, somehow, try to see it as a positive. I'm aware it must be hellish for you to go through, and all I want to do is give you a hug, but please, keep going. He loves you and you love him.