Hi pret, the problem is at least partially your timer.. a two minute burn is too much. remember the function of the timer is just to keep the fire alive.. with your boiler in a nice basement room in a new house, there is very little heat lost to radiant, like it would be in an old damp stone cellar... so your boiler doesn't loose any heat hour to hour if there is not any hot water used..
So every time the timer runs,, it bumps up the water temp, then bumps it again, and again... soon you will be at the max temp that the timer's high limit aquastat is set at and the timer won't run 'cause the water is too hot..
I'd find a timer that is settable to 30 seconds per hour, or at a minumum 1 minute per hour... my AA260 does bump up the water temp some from the timer's burns, but it's only a few degrees.. even when the outdoor boiler room is in direct 95* sun and heat... So I think you are getting too long a burn on the timer..
But if you just turn it off, then your fire will shrink to a central ball of fire, with some ashing problems .. I'd find a better timer.
It will take several days to generate ash in the ash pan.. you are just maintaining a fire right now.. BE HAPPY,, in the winter you will be emptying an ashpan every few days..
Right now I empty my ashpan every week, and it's not full... in the winter every day or two, depending on weather/temps.
It sounds like you are zeroing in on the settings... 160* high with 20* differential should work, and a one minute keep fire burn every hour or two.