I realise that's all a load of tosh and you shouldn't ever have to tiptoe around like that, but I have been there - I was in an extremely abusive relationship for a long time and I finally left. I have been suicidal too - but now I am so so glad I didn't do it
you may think you are a shit mother but you're not, and if you even think you're half a mother, surely half a mother is better than no mother at all for your 5 children
you need to get out of that relationship it sounds utterly crushing like it has removed your entire sense of self
you need to plan what you do want from your life
don't think you're mad looking at the gun thinking that, I think it's quite a common thought process, at its most innocent - eg I often look at the trains coming to my platform and think,,, I could just... step out... it would be .... just.. like... now... and it IS scary yes, but it doesn't make you crazy or a terrible person or anything at all abnormal really. No doubt you are reacting to events and your environment.
Please try and get some sleep. Tomorrow start to plan a way forward from this point. Womens Aid can help, and Samaritans do indeed email. remember you are not on your own and it's not too late and there is a whole world and life on the other side, honestly there is