My relationship is testing my mental health!

I'm just gonna lay my whole relationship out for you all to see (its very childish in parts in my opinion but this is what I've got to deal with) so.... We got together 6 and a half years ago. At the very start we were just messing around, neither of us thought it would get serious. Anyway I found out that while coming to meet me he was also messaging a 'friend' of mine arranging to go to her house for sex. So naturally I thought I was just another booty call to him and we meant nothing.. So I end up kissing someone. In time we stayed together and started getting serious, of course there were ups and downs. No relationship is perfect but we did have one thing we both stood by, and that was no adding people on social media that we didn't know very well, and no adding people that we disapproved of. You hear of social media ruining relationships all the time. Well anyway fast forward to 6 years later, we have a 4 month old baby and we're doing OK. Not perfect but we're happy... Or so I thought. We go away for the weekend, he sleeping and his phone pings. I just glance at the screen thinking it's maybe his mother asking how the trip is going. But what I find instead are notifications from these girls on instragram. Now I can deal with males having females as friends and vice versa, I'm not from the dark ages I understand you can have friends of the opposite sex. But in the 6 years of being with him I'd never heard of these girls before so the alarm bells started going off, especially since he doesn't even follow me on instragram! His own girlfriend! And he made the fuss about not adding people bla bla bla. So I ask him Wtf is he following them for.. The usual argument, and he goes very defensive. We argue and the pathetic kiss from 6 years ago gets brought up, even though he was doing wrong too at the time. Its fucking pathetic and childish. So as we're arguin he attacks me, strangles me and spits in my face! This was a few weeks ago. I've forgiven him about the attack and have since had some very bad news regarding a family member. Even though I need him now more than ever he cannot put this kiss out of his mind and is constantly having sly little digs at me. He's always muttering stuff under his breath when I walk past him, or making some cruel comments then laughing them off if I retaliate. It's literally exhausting me! I'm about to lose a parent in the next few weeks and all he can do is think about himself and how betrayed he feels. It's fucking ridiculous how he thinks he does no wrong and makes me live like I'm walking on egg shells so I dont upset him. When I mention these girls on Instagram his whole mood changes, he says they are school friends (they've never been mentioned before) so when I say ok so you won't mind if I add my old school friends that are guys because I'd like to see how they're doing after all these years. He goes crazy and He calls me every name under the sun. Degrades me, he even told me to die tonight and that he hates me. How fucking distasteful with what I'm going through atm. My mental health is at breaking point and he knows I can't leave just yet as I have nowhere to go! So basically I'm stuck here until I find somewhere, I won't go to a shelter because the only one in my area is really far out and I wouldn't be able to get my kids to school and back. Sorry for the long post. I had to get this off my chest, my head is spinning keeping all this bullshit to myself, there's loads of parts I've missed out too because I'd be here forever if I went through everything with you all. Thanks for reading if you made it this far