I could not make the DW1560 (or Lenovo) card work reliably, so I ended up using an NGFF to M.2 adapter and using an Apple (Broadcom) BT+Wifi card. Fully working out of the box, with no extra kexts needed.
This does require losing the fancy STRIX aluminum I/O shield, as the adapter and card combo are now too tall to fit within the metal box and thus under the shield.
I made a little bracket for the NGFF slot which holds the adapter solidly, while still allowing me to easily remove the card should I ever need to, and added heatsinks to the appropriate positions where the IO shield previously acted like a heatsink. All is running well, and quite happy with the entire setup.