Cook pasta according to package directions; drain and keep warm until serving.
Cut a strip of fat from bacon; dice it and render in large skillet over medium heat; remove cooked solid bacon fat pieces from skillet and set aside.
Dice remaining uncooked bacon and place in large mixing bowl. Add ground beef, onions, garlic, bread crumbs, egg, salt, cumin, black and red pepper. Mix thoroughly and shape into walnut size balls.
Cook meatballs in rendered fat in skillet until well browned on all sides.
Meanwhile, heat mushrooms and spaghetti sauce in large saucepan until simmering. With slotted spoon, remove browned meatballs from skillet and place in spaghetti sauce. Strain and discard fat from drippings in skillet, reserving onions and crusted bits, then add these and the reserved cooked solid bacon fat pieces to spaghetti sauce.
Simmer sauce and meatballs together for 20 minutes covered, stirring occasionally (if sauce is too thin leave lid slightly ajar for part of heating time to concentrate and reduce sauce.)
Serve meatballs and sauce with cooked pasta and Parmesan cheese.