Are you familiar with the phrase, "If in doubt, don't do it."?
So if you're feeling unsure about putting in your home address, then you don't have to.
There's no rules saying you must put in your home address, is there? It is your Sat Nav, you do what you want with it.
Or you could just put in the name of your town and that's it. Once you're getting closer to your hometown, your reflexes just takes over, and you'll simply drive the rest of the way to your home, because you're familiar with your local streets.
While you're worried about someone nicking your car, or your house keys with your car keys, you should also consider other risks, like what if someone take just your Sat Nav device, instead of the whole car. Wouldn't it be easier to simply grab the device and leave the car, so if you can see your car there at car park or garage, you may think it's fine, not realising crooks are using the Sat Nav to get to your home.
As for keeping house keys with car keys, I can't imagine anyone want to do that, but for the benefit of other people who may do that, my advice is don't. The risk of getting locked out of your car mean you could get locked out of your home too. Keep house key in your pocket, so if you're locked out of your car, you could hope someone gives you a ride back to your home, you get in, and get the spare car key.