Use the beds spawn table for /setspawn.

chat.lua

@@ -27,7 +27,7 @@ minetest.register_chatcommand("setspawn", {
 	func = function(name, param)
 		local player = minetest.get_player_by_name(name)
 		local pos = player:getpos()
-		fun_caves.db.spawn[name] = pos
+		beds.spawn[name] = pos
 		minetest.chat_send_player(name, 'Your spawn position has been changed.')
 	end,
 })

depends.txt

@@ -2,6 +2,7 @@ default
 flowers
 wool
 bucket
+beds
 hunger?
 mobs?
 mobs_monster?

init.lua

@@ -115,15 +115,6 @@ end
 --fun_caves.print_recipes()
 
 
-minetest.register_on_respawnplayer(function(player)
-	local name = player:get_player_name()
-	if fun_caves.db.spawn[name] then
-		player:setpos(fun_caves.db.spawn[name])
-		return true
-	end
-end)
-
-
 local hunger_mod = minetest.get_modpath("hunger")
 fun_caves.hunger_id = {}