Expanding on an adage of Confederate General Thomas 'Stonewall' Jackson in regard to taking counsel of one's fears, General George Patton is reputed to have said, “The time to take counsel of your fears is before you make an important battle decision. That's the time to listen to every fear you can imagine! When you have collected all the facts and fears and made your decision, turn off all your fears and go ahead!”
Acting on FEAR and not knowledge is one of the things that gets armed citizens in trouble a good bit of the time. It's your home, your environment, if there is any place on the face of the earth where there should not be any need to feel FEAR, your home is that place.
What you need to do is figure out some good ways to replace FEAR with knowledge. You need to find some better ways to "collect facts" before you go charging off to do battle with an unseen and unknown foe.
First thing is establishing one new habit for you and/or your wife- each night EVERY night before going to bed, CHECK THE DOORS (and any windows that might have been opened during the day) to make sure they are closed and locked. Don't close your eyes until you KNOW the doors are all closed and locked. And re-emphasize the lesson to Dear Son - DO NOT open exterior doors, ever, without you or your wife knowing he's doing it, and who's on the other side.
I would suggest you consider taking the NRA's Personal Protection In The Home class, if it's available near you. Take your wife to the class too. See
http://www.nrainstructors.org/searchcourse.aspx for a locator tool. Failing that, get a copy of the textbook at
http://materials.nrahq.org/go/product.aspx?productid=ES 26828 , and/or the DVD of the classroom portion of the course at
http://materials.nrahq.org/go/product.aspx?productid=ES 26840 .
Formulate a better plan for dealing with odd noises -or worse- in your home. The class above will help a lot in that regard. Details are up to you but now you at least have a basis to build on.
Get a dog that is NOT worthless as a watchdog. Doesn't have to be a $15,000 Schutzen-trained Malinois, but you need a dog that will at least warn you if something odd is going on near or inside your home.
Some kind of alarm system is mandatory. Doesn't have to be a professionally installed hardwired monitored system, a $100 no-fee X-10 DIY jobbie can work for you IF you'll use it.
http://www.x10.com/promotions/ds7000_19piece_hmp.html?feat6 is one source, shop around. I'd avoid motion detectors and just use magnetic reed switches on doors or windows, they're more reliable IMHO.
There's more but this is a start... hope it helps,
lpl