First off great looking Smoke! Sorry you didn't like the flavor, but that's the great thing about smoking you get to try again!
You said it best personal preference has a lot to do with the smoke flavor profile.
Hickory, like mesquite can be a bit bitter, especially on poultry, and pork. If you want to give the sausage another try go for apple, peach, cherry, pecan or a mixture of any of those.
With that said it could be your sausage too. Was it pre-seasoned, or was it straight ground pork?
In my mind spinach doesn't pair well with the pork if it's a pre-seasoned pork. And I'd probably not use provolone or cheddar, but that's just me. With beef I'd certainly use what you had in there.
How about this for a filler with pork. fennel, sautéed diced apples and onions, quinoa (pre-cooked) or stuffing. Smoked over apple wood or a cherry and pecan 50/50 mix. Oh yeah!