My thoughts...just remember this type of set up is new to me and I still consider myself as a newbe.

With that being said; Water going into fish tank from pump / sump should do a splash down into top of fish tank. Water leaving FT should be pulled from the bottom but leave the tank from the top. Water then can go into your whirlpool filter at the bottom and leave from the top. With my "Whirlpool Filter / Fry Catch, I would skip the mesh filter and enter the rest of the system as showed.

All tanks, DWC and NFT's can be at same level or on a down hill run except for the Sump which needs to be lower to allow water to fill it by gravity flow.