Your best bet is Aternos. Unless you want to create a massive server with hundreds upon thousands of visitors at a time, since servers automatically time out after five minutes of total inactivity.
Holy moly that's a lot of mods. Listen, I haven't used any of these, or have encountered this problem before, but I'd say that your problem most likely comes from "biggerstacks" since that mod is relating to stack size. If the mod has a settings menu, look through that and see if the stack size is set to one. If it doesn't, remove the mod from the pack and see what happens.
I would say that 1.13 would be the "newest" old version. I feel that the 1.14 texture overhaul is a good splitting point between eras. Even if 1.14 was the newest version, it would still feel like every version that came before was decades in the past, but I can't say for sure as I wasn't playing java edition around that time.