Esters are really fruity aromas and flavors.
Acetaldehyde is similar to fresh cut green apples. (An apple ester would smell and perhaps taste of apples, not freshly cut green ones
Diacetyl is butter or a slickness on the palate. The problem is some people are hypersensitive and other do not detect it at all. I'm middle of the road which is good, if you are at one end or the other, just figure out where and IMO judge as if you were in the middle.
Astringency is as I described above. Think of sucking on a tea bag, ignore the flavor, but what you are after is the sensation in the mouth.
I think your temps are minus 100 for the fermenter. If your fermometer is not exceeding 68F, then are you perhaps pitching above fermentation temp and allowing the temp to drop. Starting at say 90F? Esters are formed early in fermentation and yeast loves a high temp since they really want to make alcohol and CO2, not necessarily a tasty beverage unless controlled.