Interesting that your psa was lower on the 3rd test. Your next will be your 6th, could that be lower? It's a slow rise which isn't a bad thing. The up and down could be a sign it's inflammation, but I'm not at all qualified to say that.
You ask if you should ask for an MRI and then got involved in a debate about the quality of the equipment. Also whether to have a TRUS or a template biopsy. Less than 2yrs ago I had a TRUS then an MRI. They were very quick with the MRI, 3 days, and then about 5 days to the result. Whereas the biopsy took a week and the result 2 weeks. So perhaps if you have an MRI you could know something in just over a week, whereas the biopsy could be nearly 3 weeks.
Alternatively there is a lot said about over treatment and many doctors want to find genuine signs. Some say that PCa is often a slow disease where you can wait. Your psa isn't that high and it isn't rising that fast so you could have time to make decisions that take a bit longer. On the other hand that's a personal decision about risk. The low risk decision could be to have the TRUS and if it finds nothing then have a template biopsy and/or an MRI. You might have just an enlarged prostate. I hung onto that idea for a few weeks with a psa of 9 as I seem to recall the stats said I'd a 40% chance of it being benign which seemed quite decent odds.
So you could go with the flow or ask for an MRI as long as the dates aren't too long. Theoretically they have 30 days to diagnose you from the day the GP referred you.
These notes start off short but grow, I hope it makes sense.