I'm not sure why YOU should be scared. Whether he succeeds at what he needs to do is entirely in his hands. I think it would be best to KNOW if he's jerking you (and the system) around, or whether he is approaching this with the seriousness it deserves.
I can already see that you are going to be ready to blame the system (the judge, his probation officer, his treating professionals) for being "too hard" on him, when it's only by their good grace he's even got the opportunity he HAS. By rights, he SHOULD be serving a prison sentence.
So will he take advantage of the opportunity? Or will he just go through the motions and wind up in worse trouble next time? And what will THAT mean, for you? Will it be because he does something (else) awful to you?
If the probation officer is "doom and gloom" it's because your husband has not given anyone reason to think he's interested in changing.