I don't know how much more i can take

Earlier this summer my 11 yr old & 13 yr old decided they were going to sneak out of the house with a "friend" who I had told them to stay away from. told them he was trouble. Of course i'm  just mom what do I know, turns out I know more than they thought. they were out way after curfew & instead of just talking to the cops & coming home they ran from the cops. The cops caught them & all 3 confessed to slashing tires. they all wrote a statement & then the 2 officers took my 13 yr old & the other kid out in 2 separate cars the other kid confessed to a majority of all the tires while saying my 13 yr old did 1 or 2 & my 11 yr old was just there. A lot of good that did I'm stuck with coming up with 2/3 of the damages almost $500. needless to say I am now looking for a 2nd job, it's a chore just to get to my 1st job. I thought that after we met with the states attorney & he explained everything to them & what had to be done to keep this out of court, I thought they were finally understanding. then today happened! I was kind of feeling better & thought I was finally coming out of this episode but then I got the call from my 13 yr olds school "ms d we cannot let him come home on the bus & we need you to come to the school immediately. we need to have a conference about a situation that happened." I get there we talk I find out that he took a pocket knife (which I had already taken away) & a lighter to school. right now he is suspended from school for at least 6 days, once they finish their investigation into his intent if any ( he says no intent, just forgot it was in his bag. he stayed at my parents this weekend) they will let me know if it stays at 6 days or if it will be longer or worse.
on Saturday night my mom let my oldest son spend the night at his friends house which is normally no big deal. the big deal was when he called me Sunday morning to pick him up he was still with that friend but they had walked to someone else's house ( again someone I told him to stay away from). My problem with this other "friend" whose they walked to was he along with some of his friends got my son started on pot.  I know he's still using occasionally , not as much as he was.  I don't think he used there yesterday but I'm no certain. I just feel that every time I think that i'm feeling better & coming out of this depression my family ( not just my kids, in time I will open up more) just pushes me back down. I don't know how much more I can handle. sometimes I just want everything to end.