Concerning losing slots while you have weapons equipped, the first note on Page 21 of the Eternity rulebook states: "Some boss cards may result in you losing slots. This does not affect the number of weapons you currently have equipped, only how many you may have equipped on your next turn. If you start the turn with more equipped weapons than you have slots, you must attack with your weapons until that is not the case." So, you don't need to immediately discard any weapons when your number of slots is reduced.