Chances are the seller may have ruined the other plates as well. The exposed plates look in good condition so you could try them you shouldn't need an anti fogging agent - it's not recommeneded with films as it'll cut the speed and you can print through any base fog anyway. Just checked and it was euqivalent to 50 ISO so tyr it at 25 EI
I doubt you'd get modern photopapers to fit with a glass plate as well, unfortunately Single weight papers disappeared some time ago but it's worth a try, some thin card may be better. 9x12 films eay to get as it's still a common European size.