Welcome! Sorry for the news. Actually your intro is quite a bit shorter than most and the more info the better.
Just my observations/opinions based on my personal experience and information gained over the years.

I was in a fairly similar situation to you. At 69 years old had rising PSA, biopsy revealed G9. Had Robotic prostatectomy. Six months later a PSMA PET revealed a solitary T8 met treated with radiation (SBRT) with good result. PSA continued to rise so had another PSMA PET 4 months later with positive node in pelvis. Sought consultation with Medical Oncologist (MO) at Johns Hopkins and was immediately treated with triplet therapy-ADT/Lupron, Chemo (Doxetaxel) and Anti androgen receptor/Darolutamide. Rapid response with PSA undetectable (11/22) and has remained so since. After the triplet therapy I had 37 radiation treatments to my pelvis with boost to the positive node and prostate bed.

Many MO are getting aggressive with oligo metastatic (limited mets < 5) disease. At your age, some suggest a prostatectomy to remove the significant majority of the tumor. Then follow with triplet therapy (ADT started immediately after the PET ) and radiation to your pelvis. That's probably the best chance for cure ( they don't know yet if oligo can be cured but some believe it can in some patients) or long term remission.

As one poster said, your history is complicated by your other cancers. Best advise is to get a very experienced Team at a Center of Excellence where they treat a lot of prostate cancer.

Good luck!