Hello terpjr
You have a really good question there. I'm not a fan of infra red thermometer either. They Work good on engine exhausts to check individual cylinder output temps. And eng temps. Yes the temp wells are very good and that is what I put on all my furnaces.
It is important to make sure your heat exchanger is set up to counter flow the water ⏫⏬ !!
Assessing efficiency. Can be done but it needs to be broken down into compartments,
The btu requirements for the house or heat load. (Will change with temperature of course).
Btu loss to the house. (Underground pipe type and size. )
The efficiency of the heating unit. I like MLappins analysis on wood consumption.
if the house is comfortable and warm all winter. And the boiler is at 180deg F are you comfortable with cutting and handling all the wood that is not going to your house.
I am in the Albany area often and would stop in to look at your system.
Or you could stop up and have a look at the G-200 in action. I'm just above Saratoga.
I have to go to freehold NY to do a heat exchanger set up. That was done wrong. So I will be going by that area. You can call me. Or pm me.