That is how my tank is plumbed.
Flow through the fuge should be much slower so the macro can work efficiently.
TEE off the return and put a valve right after so you can control the flow into the fuge.
You could easily TEE off the return.
The lengths of the return should be as close to equal as possible to ensure equal flow to the DT.
That sump looks easy to plumb but remember you need to support your plumbing with clamps. I would get clamps slightly larger than the tubing and place some foam between the clamp and the tubing to isolate noise.
A cut up mouse pad is perfect.