I think in the comic they actually find an armory with supplies for re-using casings, adding powder, etc, but all in all, yeah, they should be throwing rocks at each other or using blunderbusses by now...
Regarding, Negan, I have mixed feelings about the loss of the beard too... JD Morgan isn't quite physically imposing enough to be Negan, but he makes up for it with his acting chops. He did seem more menacing with the beard tho'... oh well.
You never know who the show will choose to kill or not -- it seems like they are sort of trying to make sure people alive at this point stay alive and people who were supposed to be dead are eliminated (Abraham, for example, was killed by a crossbow bolt in the comic, well before the Glen execution, but in the end, he's still dead at this point).
As to Eugene,
well, I'm sure somebody else can learn to make bullets if he doesn't make it back...