Welcome to Healing Well and I am Kitt.
All three of the scenarios you posted may be right.
Since PSA is produced by both normal and cancer cells in the prostate, if all prostate cells have been removed at the operation, then the level of PSA ought to fall to almost zero, or less than 0.1 ng/ml. The time taken for the PSA to drop to this level after surgery depends on how high it was before the operation; however, in most cases, it should be undetectable at 3 months after surgery.
Most surgeons recommend measuring the PSA once every 3 - 4 months after surgery for the first 2 years and then 4 - 6 monthly for 2 - 5 years. After this, the risk of the cancer returning is small. Annual testing is then recommended. Your doctor may suggest a different testing program, however. It very much depends on the nature of your cancer.
Keep posting, we are here to support you. Again Welcome.
Depression 25 years, Husband Crohns Disease 30 years
"If you doubt you can accomplish something, then you can’t accomplish it. You have to have confidence in your ability, and then be tough enough to follow through.”