Hook HAM_Spawn and give user godmode if he has the "spawn protection item" every time he spawns.
Also I suggest using pcvars instead of get_cvar_... They are way faster.
You can also cache cvars every round or in plugin init, that would be the better way.
Also you might want to define a task id and use it id + TASKID. You are using user's id as task's id. As a result if other plugins have such task id could conflict.