A violation of a 50(b) Domestic Violence Protective Order is a class A1 misdemeanor. The punishment he receives depends on the judge and the extent of his prior record, but the most he could get is 150 days in jail. He could also receive a suspended sentence.
No answer to these questions is intended to, nor does it, create an attorney-client relationship. There is no substitute for an actual conversation with a licensed attorney about the particular facts and circumstances of your case.
The only thing I would add is that the maximum punishment is 150 days for EACH offense. So if your husband has been charged for the letter and the 3rd party contact, then he could be punished for each one. That depends on how he has been charged, it at all. The AOF he has been convicted of guarantees that he is at least a level two, which means he is eligible for a sentence of up to 75 days. However, again, these are all maximums, and as has been stated, he is eligible for probation. That said, judges are generally not happy about violating orders, and take that into account.