Yeah Ik it can get expensive but once you have everything set up right it will only be food your buying. I wouldn't get the same thermometer again bc if they are calibrated the same they could both be giving inaccurate readings. I would look around and read reviews on others with probes and get one with good reviews and then compare to the one you have. Another option would be a good ir temp gun. That way you can take the temp anywhere with a click of a button.
Yes I seen that you said your thermostat is all the way up but if you can't get a temp high enough you may have to buy a new one that let's you set your temp higher.