Need help/questions answered setting and understanding my basic boiler parameters

dbsoccer

I am working to fine tune and understand my boiler's basic parameter. I have a 38-year old natural gas fired Burnham XG2000 PV. It has worked fine over the years but, as expected, has needed some common maintenance repairs (blower, expansion tank, etc.). In the course of these repairs I installed a Watts RBFF and I upgraded the included Watts pressure gauge.

The boil resides on the first floor of my two story home. There is a small heated basement. The fill valve is set to 15psi. Today I checked and re-set the expansion tank pressure to match.

I'm not a cell phone guy but using a cell phone and a selfie stick I can now take a picture of, so to read, the temperature gauge on the side of boiler that is otherwise extremely difficult to see due to how the unit is installed.

So my questions are:

1. Is 15psi too high for my installation or should I reduce the pressures to 12psi.
2. As the boiler reaches it maximum operating temperature what sort of system pressures should I expect see (per the gauge on the RBFF)?
3. Now that I have a means to read the temperature gauge what are reasonable numbers as the boiler reaches maximum?

Thanks for your help.