Hi and welcome ALanger
Noone here can really tell you if you're wasting your time or not - many of us do have a moment of clarity and recover, others don't...some get that clarity as young people, others don't.
I think you need to consider your 11 yos welfare in this.
If you have any doubts about her safety or her proximity to things you don't want her to be around then I think your way is pretty clear.
If your son is using and continues to use, I think his probation officers suggestion is a pretty good one.
If your son continued use of drugs results in him being arrested or otherwise having to leave your house,. his actions will have precipitated that.
I understand your fear of suicide - I don;t know your son or whether he';s said things that lead you to fear that might happen, but many addicts actually use that as a bargaining tool - the folks in our Friends and Family forums call that quacking -
https://www.soberrecovery.com/forums...king-mean.html (What does "quacking" mean?)
the reality is you have a 11yo child in your care, I think that should be the priority right now.
D