If I'm reading all you are saying, you are starting out with thermal. I've been there myself, not too long ago, back in April 2014 ... at first I couldn't tell a deer from a turkey, at 200 yards !
I'd read I would need a lot of experience to be able to "interpret" what I was seeing with the thermal ... and I think that is true ... but the "levels" come in spurts ... but watching the critters move and night and categorizing all that is much of this "interpretation" part.
I'd say, for me PID is 60% how they move, 30% shape and 10% other ...
Like if it jumped a fence ... it is more likely to be a deer than a coyote !
The "heads down grazing" behavior is also very abnormal for a yote ...
Opossum versus Coon ... head on can be tough ... Coons usually move faster, but not always ...
Even recently I thought a yote was a deer because it was eating apples off the apple trees in the apple orchard and I've seen 100 deer do that, but zero yotes ... but eventually I figured it out. Size was the first clue, but when it started moving away from the apple tree, then it was obvious.
We live along a creek and there is a lot of vegetation, so often I am doing PID through layers of vegetation, even in winter with a zillion dead weed stalks. Around here "weeds" can be over your head with stalks thicker than your fingers and so hard it would take 5 mins to saws through the stalk with a serrated pocket knife.
But stick within and things improve a lot !!!
Also, usually for me on black hot, the ground is white and the critters are black, and that's whether snow on it or not. When I've put up black hot videos, some people have commented about the "snow" even though there was no snow.