small you need to talk to someoone in real life - your tutor, can s/he refer you to college counsellor? might be quicker than GP route.
you need to see a solicitor to talk through separation issues/who owns what/what finances he has/you have etc.
i had a not dissimilar situation - exP got stressed/depressed. more and more angry at everything/life, i trod on eggshells, he began talking in 2005 about "life not worth living", pushed me couple times etc....2007 he exploded literally, attacking me and my ds(who is autistic)...short story - got him to leave to his family - he came back to "visit the DC" at xmas 2007 on basis he would stay for 2 weeks...then refussed to leave and in in early 2008 i was in v similar position to you - with him blaming me for everything, GP "colluding" etc...so finally lightbulb moment - i talked to woemns aid etc, people were saying to me refuge - but i ahd a job/income so i did up and leave with DC to rented accomodation in april 2008.
it hasnt been the end of the story - it has been a long road to get distance emotionally - he is, currently, back in v depressed phase and anxiety (have had to cut contact with children - again).
but as was said - it is not my responsibility.
that is something to repeat like mantra - his issues are his responsibility.
his mental health is his responsibility.
if he makes the choice to kill himself - his responsibility and nothing you can do can change that - (the nhumber of times i have planned his post-suicide funeral in my head...)
but far better he does it while you and DC have made another life elsewhere.
my Dc are relaxed, happy - took a while - but over time they have settled so much and our place is a haven of peace...
his anger /depression has continued - it was nothing to do with me however much he makes it out to be so. he thought he was entitled to use it on me...
think practically: where could you go? could you rent?
could he go elsewhere? family/friends - even say to him at least for now...give you some breathing space...
at 8 and 10 your DC are seeing and hearing stuff - my DD was 8 when we left and she was far more affected as she understood and saw so much more than youngest who was 5 .
(oldest ahs leanring disabilities so is different matter - but also has settled wwell)
your repsonsibility is to you and to your DC - because you alredy do most things for them (as i did) and this home is not good...yes it is hard to realise but realise you must. speak to RL friends, get support, think practically how you can move out or how to get him out of your house...
thing is you cannot be responsible for his MH. it is up to him. it sounds cruel to cut someone out of your life when they down - but when they been aggresive/bullying/blaming (and violent) towards you is only way .
if you leave he may or may not get the help he needs - but while he making your life a misery you have to set boundaries. he goes or you go . for the sake of your DC.
you say "he has always had a temper". whatever has triggered the depression, however bad his back - you done your bit of trying to support him. no more.