You will get two coupons in any case, as one is required for each flight you take. it sounds as if you’re over-thinking things - you’ll get exactly the same result whether you click on ‘multi-city’ or not. To split it, you need to make two separate bookings.

Baggage will be through-checked if booked on the same itinerary and the connection is under 24 hours. If overnight you can ask for it to be short-checked.