Covering food is just normal for some cats. Living out the world for instance, a momcat that has just had a litter will find a huge cache of food, she will eat what she can and bury the rest for later. Come back dig it up and bury what is left in another place. Perhaps you are feeding to much food? My vet is fond of saying "feed the cat, not the bowl."
Stinky gas can be caused by low-grade food, or impacted anal glands, or another health problem.
Scooting the rump on the carpet means either parasites or impacted glands. Sounds like your cat needs a vet visit.