How would I go about deleting a variable’s contents if it’s a game object WITHOUT destroying the variable?
In this case it’s an instance of a prefab. How would I delete it ? I wouldn’t want said object to hang around forever.

I don’t understand what you are talking about here- it is impossible to destroy a variable! A variable is a named link to some other object- if you delete a variable’s contents, the variable itself will still exist, except that its contents will become ‘null’.

As for slotted weapons, do you want the player to be able to drop weapons and pick them up later? Or do you use a separate ‘pickup’ object for that? If you are talking about the weapons that a player actually uses, why not just not delete them at all? Just make them invisible until your player wants to use that particular weapon again, and if they’re not carrying the right token (“game logic” weapon, as opposed to graphics etc. weapon), then just don’t let them take it out.