CambuiAl ... I sure like your cooking grate.
I too have been having issues with thermometers so I bit the bullet and ordered a Maverick ET732 and will get yet another turkey thermometer and start over. I figured that 90 to 110* difference was too great between center and outside, Maybe not.
Small Charbroiller, 40 year old barrel pit, UDS, 97 Weber Performer, Brinkman gas grill.