that's fairly normal 10PSI below dripping on the relief not that that is so accurate place a plastic bucket under it so to see if water drips...your good...i have a metal tank mounted above a one level cape cod pipe comes off the supply out of a weil mclean hot water baseboard system has a drain cock on it no bladder and drainable(isolating valve. simple expansion might consider that...180F water on bladders under pressure....take the wife to dinner instead...normal PSI..cold boiler sits at the RED regulator feed typical 12PSI then heats to 180F as yours 20psi stat satisfies...might want to lower that limit to 160F see if you satisfy the house control is very liberal TO SEE ACTUAL SETPOINT when the main gas shuts off but the circ pump stays ON
that is your control setting no matter what the dial says...cheat a little hand out some swets and long johns
keep in mind what water temp to you need to make 70F setting. wind blowing below 30F boiler will run longer during to wind chill treat the troops to a reset up.if you turn the limit scontrol just after it goes off with the circ on you'll se the main burner wil light that is the temp check the thermometer.... on the boiler.