Player getting kicked from Minecraft server the moment player gets their inventory?
Since it's their inventory causing a disconnect, I would delete the player nbt data from the world file. That does cause the inventory data to be lost, but it's hopefully better than not being able to play at all.
As for your not being able to host locally problem, take a look at ngrok. It's a port tunneling service, so you can set it up, tunnel tcp 25565, and you'll be able to connect to the IP it gives you.