If he violated and only got 90 days, he's lucky. Violators usually have to serve their time in the jurisdiction they were sentenced.

You can call the mail room at the facility and ask them directly if your inmate is receiving the mail you sent

You cannot call an inmate, they must initiate the call.

yes

You shouldn't visit, but him calling you shouldn't raise any red flags

Punishment for not following orders. Inmates are not free to object to much to the way they are handled by the 'system'.

Usually within the first week unless they are overbooked with new inmates, then the process is a little slower

Furloughs are only granted to inmates with a perfect record and relatively short time left remaining on their sentence. You can call the facility and ask to speak to your inmate's counselor or case manager to see if he qualifies.

2-3 business days usually. if there is a holdup, it is in the facility mail room as they inspect every piece of mail before distributing them to the inmates

No, but there are bad apples everywhere. Inmates need to mind their business so the dirty ones stay away...