I have a Mini-Therm hot water boiler that no longer comes on when the
thermostat calls for it. I have to push an ignition button each time
including ~4am when the temp in the house goes below 62 degrees. The
boiler also shuts itself off before the desired temperature is reached
and I have to manually restart it each time. This has ended up being
about 10+ times a day during really cold weather and is getting
tiresome.

I've also noticed the water pressure is only at 15 psi. Isn't it
supposed to be at 30 psi?

I've bled all of the upstairs radiators with the boiler on (which is
what the previous owner told me) and got a small amount of air out of
each one but when I opened one of the radiators in the basement, there
was no valve to bleed it. I stopped at this point since the other 2
radiators downstairs are currently painted shut.

Any suggestions? Where should I start?