Hi Starr from NW USA, and welcome.
The decision to move forward with a biopsy or not is a bit cloudy with the information you have so far. Indeed, a positive biopsy is the only way to really confirm that you do have some degree of prostate cancer, but on the other hand if you only have a tiny bit of PC (which may or may not need to be aggressively treated), then you should also be aware that the biopsy is simply a "sampling" process which may miss PC cells. PC cells tend to grow in clumps, around a focal point rather than be homogeneous like cream in coffee.
You've gotten some good inputs already. Here's one to consider from the American Urological Association (LINK):
"...the decision to proceed to prostate biopsy should be based primarily on PSA and Digital Rectal Examination (DRE) results, but should take into account multiple factors including free and total PSA, patient age, PSA velocity, PSA density, family history, ethnicity, prior biopsy history and comorbidities."
The "free PSA" (PSA-f or FPSA) test measures the proportion (%) of free PSA to bound PSA in the total PSA in your blood sample...the test you alread had is called the "total PSA" test. The "free PSA" test is called this because PSA-f circulates in the bloodstream "unbound," without a carrier protein. That might be more info than you need for now, but know that high free PSA -- above 25% -- usually indicates BPH (benign prostate hyperplasia) which is a benign prostate issue which increases PSA. On the other hand, low free PSA likely signals prostate cancer. Most men with prostate cancer almost always have a free PSA below 15%.
Your urologist can administer this test...it's done with the same blood draw as a "total PSA" test.
Also, you surely are having some infection issues which cloud your total PSA result, as evidenced in your decline in the follow-up 2011 test. Did the doc prescribe antibiotics?
For your age, your PSA is a bit high...but please do keep in mind (with regard to your comment about treating clinicially insignificant PC...which is a very astute comment) that just because you might find out that you have a prostate cancer doesn't automatically mean that you need to jump into an aggressive treatment. A good doctor might tell you to "wait, and lets see what's going on" before aggressively treating. Make sure your diet is focused on not eating things that promote cancer, and eating things that help fight cancer; and, make sure to also fight cancers with a good exercise program. If you do proceed with biopsy and you do find a very small amount of low-grade cancer (a common finding), some men (participants in scientific studies) are able to keep it from progressing through diet and exercise...and have improved their quality of life by doing so!