It's a hard one when you are a single mum trying to do the best for your kids. I have an autistic son 14 and autistic daughter 25 (still lives at home as is too immature to live alone) and I often find myself wondering if I have done them any favours in 'overprotecting' them. However, at the end of the day no one is perfect, and a 'good mum' loves her children and does what she thinks is best for them. No one else has the right to say otherwise.
Your partner sounds as though he reached the end of his patience, as you were stroppy with him, and said something about the one thing he knew would hurt you most, your parenting. To be honest, in an argument, people will often say things they regret later, but men especially, are not good at owning up and apologising. He also probably feels like you started it and, therefore, you should finish it.
You have a huge amount going on at the moment and it's difficult to keep calm in such situations. It sounds to me like you could do with some counselling. I see mine once a week and just being able to talk about anything is amazing - allows you to calm down completely so that you can be relaxed everywhere else.
As for texting him, do you really love him? Think carefully about this, because it is easy to blurt out, well of course I do, but I realised with my first husband that actually I didn't, so I left. If you really do and you miss him, then bite the bullet, text him and apologise. Say you realise you have been hard on him but that you do love him and are really sorry. Don't bother with reasons for your bad temper - he surely knows what is happening to you regarding work etc, and it never helps, making excuses.
Don;t be tempted to bombard him with texts, just the one, and leave the ball in his court.
Good luck with getting away from the bullying, and I hope you find a much better job. Also hope your DS's health problems are sorted soon.
Unfortunately, when the valve finally blows it is always the nearest person that gets the fallout, whether or not they deserve it. Don't beat yourself up, you are doing the right thing with work and once that is sorted everything else will become so much easier to deal with.
Best wishes and good luck.