Trish, my sister went through this. It's hard - very hard. She needed firmer boundaries than a mother could give - well, our mother anyway. I think mothers are softer generally though, boys need a tougher role model. You sound like you have done brilliantly given the circumstances and it's time the boys' father got involved; the boys will react differently to him (not because he's a better parent or any such guff, because he's a DIFFERENT parent) and hopefully it will help calm Brandon a bit.

As for
As a mother shouldn't I be supporting and loving them, not showing them that when the going get's really tough your out !!
You are loving them by doing the best thing for them - and atm the best thing for Brandon is to learn that if he cr@ps up his life then it's his responsibility, not yours. You are his mother, but he is old enough now to know not to bunk off and steal; he's not a todder and it's up to him to sort things out now. Yes, you can help, but he has to realise it's up to him to look after his life now.