Not sure how much help I can be as only just going through the testing stage myself. Others on here will have way more knowledge but I assume it will be a case of regular PSA blood tests and possibly more scans in the future.
From the point of view of whether it is contained in the prostate or not, I had a clear CT scan and due to this I am having to have a PSMA Pet scan (today as it happens) to confirm no spread.
You don't mention how Dad got to this stage, what triggered the conclusion he has Prostate cancer?