How can I improve my barbecue sauce recipe?
I use a similar recipe, unfortunately I don't remember the original source, but I've changed over time anyway.

Things I don't use that you have in your recipe:


Sugar
Jack Daniels
Cider Vinegar
Worcestershire sauce
mustard


Things I do use:


Lots of fresh ground spices. Typically 4 or 5 cloves, teaspoon of cumin seeds, tablespoon of fennel seeds, black pepper and salt. 
Fresh herbs, including Rosemary, Bay and thyme
Balsamic vinegar - about half a bottle of inexpensive stuff
Orange zest - zest of one whole orange
Smoked Paprika - about 4 heaped teaspoons
Olive oil - about 4 tablespoons


grind-up the spices and place in the marinade tray. medium fine chop the fresh herbs (leave the fresh bay leaves whole) with the orange zest and a whole bulb of garlic, then add to the spice mixture. To that add juice from an orange, the Balsamic, followed by the ketchup and olive oil. Mix well.

Score the meat well and add to the marinade tray. rub the marinade mixture into all the scores so that the meat is well penetrated.

Cover the tray with foil and cook in an oven for about an hour (depends on the meat and the amount) once it's out of the oven it can be placed on the barby.