You can also get a cat they will kill the mice but then if they decide they don't want to eat them they will just leave them lay and then you have to pick them up.
Go to your local health dept and go to the dept that deals with food management and they should be able to help you get a copy of yours.
Leave food and water out around the cage and look under and behind stuff especially like the refrigerator and stove and freezer. They like to hide and come out after dark.
You need to take it to your humane society or a pet cemetery in your area or dig a hole about 8 feet deep and bury it or you can go get it cremated and keep its ashes.
Your dog is probably hurting and in lots of pain you might not be able to see it cause it might be internal. You need to take it to your vet.
It should be around 160.
It depends on what kind and where you get it. Here where I live they range from around 10.00=18.00
Situps are a great way to lose weight cause it works on the stomach muscles.