Jon: all your questions could be answered before you even ask, by just getting a current 2019 U S COINS "RED BOOK". By reading all the Cents historical data you would have answered your own questions. Don't jump on LooseChange cuz I'm sure he was just trying to tell you what was the highest % of copper content cents was in the past. For your info, per Red Book, the wheat cents 1909 thru 1981 are 3.11g 95% copper, the 1982s are split part of the year was copper @ 3.11 grams, later in the year they went to zinc @ 2.5 grams. I hoard my coppers and separate my 82s via a gram scale, takes the guess work out of the formula.
FYI, currently it is still ILLEGAL to melt down copper pennies. To save the coppers is solely up to YOU, nobody is asking you to do it, and it's not going to be a get rich hobby either, so I think you owe LooseChange an apology for trying to answer your vague question. Like I said, GET A RED BOOK & read it.