YES! it would be creepy not to; just having a dead gerbil sitting there. YUK!
yes gerbil should aways have wheels with them
Buy a cat...
Depends about the dog and gerbil. You should bring your gerbil to a vet (if they do gerbils).
feed it. But seriously, if the gerbil refuses to eat, perhaps try different gerbil-firendly foods. And if all else fails, see a vet. If the gerbil will not eat, you may want to see a veterinarian. The gerbil might have a tooth that is bothering him.
It is possible. a hamster should not be kept with a gerbil. The hamster may also try kill the gerbil if it dislikes it.
no questions asked take your gerbil to the vets straight away
WHY is there wax on your gerbil? If hot wax fell on your gerbil its probably burned. You should take it to a vet.
No
Average adult gerbil weighs about 2.5 oz
you don't need to if you have another gerbil because they clean each other :)
Yes, it is possible and likely that the cat would try to catch, kill and maybe eat the gerbil. You should keep the gerbil in a cage that isn't accessible by the cat.
It is likely your gerbil died of natural causes and the other one was just disposing of its body. It is not very nice to think on but makes a lot of sense in the wild as a dead body would just attract predators.