The bad thing is I did not have the door from the garage to the house locked. I will from now on!
Aha! Now you have a plan (maybe).
You say you took up a position at the top of the stairs. Isn't that the other end of the fatal funnel you are hoping a BG gets trapped in?
I have a mental image of you standing at the top of the stairs, where you have no cover and darned little concealment. While wallboard and 2x4s to not offer much in the way of cover, you get "better than nothing" when you are prone on the hallway floor with just a portion of your head peeking down the stairs.
So you have 2-way communication with the alarm monitoring station? How much longer will it take them to assess sounds from a dropped phone or a wall unit and then contact your local PD? Seems to me you are adding more time to "when you need the police they are minutes away". Talk to your local PD/9-1-1 dispatcher (sometimes they are not in the same agency) to see how they feel about getting a call as soon as the alarm goes off so that they can at least stage response units.
And that 2-way communication hook-up? Is it based on a landline connection? A cable connection along with your internet and phone and cable bundle? Both of those can be defeated with a pair of wirecutters, whereas a cell phone needs a tower taken down to be put out of commission.
You went down the stairs to clear your house? Your wife remained at the top of the stairs with her .38 to "cover" you? How far can you go before you are out of sight of the wife? How would you wife communicate with the alarm company or the local PD if she heard sounds like you getting shot or falling over one of the kids' toys and hitting your head on the side of the coffee table that knocks you unconsious? But since nothing like either of those two possibilities happened, what's your "all clear, hubby coming back upstairs" code phrase? What's the "I'm being held captive but they want me to tell you everythiong is OK so they can come upstairs to get you and the kids too" code phrase?
Do you have an "abandon ship" drill and a rally point? How long do they wait at the rally point before deciding you probably are not coming? What do they do if that's what they decide?
In all seriousness, you did good regarding what you did - except for that clearing the house part. I just want you to think your plan out a bit beyond the immediate action when the alarm goes off. Folks that do think their plan out to the point of having to leave the house usually never need to carry the plan out that far. But if it became necessary, having a plan that goes that far is better than trying to wing it on the fly.
stay safe.