Note that having Flying Blue Gold status (AF/KL) does not grant access to DL Sky Clubs when flying domestic flights. You must have an international Skyteam itin (or connect to/from international Skyteam itin on Skyteam carriers) for Sky Club access. Caribbean flights are excluded from "international" definition for lounge access. Also, you won't have comp access to DL Comfort+ seats as an FB Elite (except possibly on day of departure) as they book into a separate fare class on DL and are not just extra legroom seats in Main Cabin. The main benefits would basically be limited to Sky Priority check-in/security/boarding, comp checked luggage, and comp access to Delta Preferred seats (exit row/aisle).