Honestly I have it set the same. 200 h/180l 20 diff and the thing is running great. Heat is at 60 and for the last week with temps dipping into the 30s I only had one can of ashes. Fire hasn't gone out and I spoke to an acquaintance HVAC repairman and first gave me detailed options as you all have suggested (So kindly!!) and then when I spoke to him again he said leave it as it is because it works.. :/
The thing is is it's not really broken.. so I don't want to call in a repairman.
It seems like something is wrong with the timer.. but not really.. When I turn the low to 160 and the diff to 10 the timer doesn't work. The stoker won't kick on for 3 hours... and when I set the diff to 20 and the low to 180 the timer kicks on because the furnace will only run between 2 and three minutes every hour with no water demand.. unless the furnace only needs to run that long when the water temp goes down, which does not make sense and is boggling.
I will update over the next few days if I can talk to anyone. I have an old school friend that took over his father's business of p&h and if I see him I'll ask him to stop by.
For right now, "if it's not broke, don't fix it" is ringing clear to me.