Hi Richard,
Just a few thoughts:
The fact that your dad's lymph node/s are enlarged doesn't necessarily mean that the cancer has spread to them.
I had a similar enlargement of lymph node/s. Initially my consultant said he thought it was probablly PCa that had spread to my lymph nodes and he expected the lymph nodes to shrink while I was on HT, because HT causes PCa tumours to shrink, and it follows that the PCa in the lymph nodes would also shrink.
After 6 months on HT a second scan showed my lymph nodes were as enlarged as ever, so I had an operation PLND (Pelvic Lymph Node Disection) where the consultant removed 12 of my lymph nodes, subsequent examination revealled these were benign.
Now your dad's PSA is higher than mine was, and the fact that they are putting him on chemotherapy suggests that they think it may have spread, however I guess he will have subsequent scans and one of the things his doctors will be looking for is whether his enlarged nodes shrink.
Having said all that PLND is not for the feint hearted, if you think of the lymph system as the bodies drains, then the lymph nodes are like waste traps. When discussing it with my doctor I said that if I was to take waste traps out of my house's drainage system I would be left with a mess. He sort of poo pooed that analogy, however a few months after PLND I was sufferring from lymphoceles, which are basically big puddles of lymph fluid that form within the body where nodes are removed, getting these sorted out involved going into hospital where the doctor used the biggest horse needle I have ever seen, which he stuck into me, slowly and carefully, watching a simultaneous scan to make sure he didn't puncture my gut, and slowly drawing off the fluid. But even then I ended up back on the Urology ward with infections.
Anyway we are all different, and it looks like your Dad's doctors are pretty sure that they know what they are dealing with, but it might serve you well to bear in mind that enlarged nodes can be benign.
:)
Dave