Can they bring up dropped charges if he got in trouble again?

Yes.

Yes they can do that if the statute of limitations has not run on the original offense, "they" being the prosecutor's office, not the Judge. There is a range of what can happen and it depends on several factors "we" don't know, and shouldn't be posted on a public site. Consult a local criminal defense attorney. Good luck!

Yes, unless the prior 'dropped' offenses were misdemeanors, or if felonies they are now outside the statute of limitation, the DA can, and the Judge will, allow the dropped case to be re-filed. Isn't that exactly what the DA told your son would happen if he didn't stay clean.

Yes. They can file the charges. If they previously filed and dismissed a misdemeanor theft charge, then they cannot re-file.

Not if it was a misdemeanor and dismissed with prejudice. If it was a felony, they can re-file it once even after it was dismissed.

Yes, assuming that the charges in August were not dismissed with prejudice (very doubtful). Without knowing the exact nature of the prior theft charges, and whether or not these are felonies or misdemeanors, and what, if any, prior criminal history he might have, his age, and the facts of the case(s), it is impossible to give you an exact answer to how much time he is looking at. The 460b - second degree burglary - as a felony, carries a maximum of 3 years. Now, since the new realignment law effective this past October, this is probably a "county jail felony," but again, more information is needed to make an exact assessment. Consult with a criminal defense attorney and lay out all the information and I'm sure you'll get the answers.

It is very possible that "dropped charges" or un-filed charges may be filed later if the cops have additional evidence and your son was not "in jeopardy" re these charges before. His 460b (2nd degree Burglary) charge could result in one year in county jail or even state prison.