Wow. LOTS of input on this thread.
I forgot to mention another important security feature we recently installed.
Sheer + Opaque curtains. I originally had wanted metal mini blinds - it's what I grew up with but my wife was used to curtains. We'd talked about them before so we went to get curtains and she chose a few favorite colors/designs and we decided out of those. We use the sheer curtains during the day, and close the opaque ones at/near dark. Just to test how it looked without them I went outside at night when just the sheer curtains were drawn shut and I could count the number of people in the painting hanging across the room. You could pretty much see anything. With the opaque curtain visibility was down to nothing. This was for the big living room window which is a plus during the daytime. The house also came with old nasty opaque dark red curtains for the bay window in the den that we flipped (we see the white side) that we draw shut during the night time. Otherwise anyone can see everything.
I don't know how things are over there but there is a lot more privacy after we installed those. The previous owner had an awning but no curtains.
You're off to a great start.
About the 9mm being a poor choice for a beginner - the first handgun I shot was a CZ75b. I hadn't had any formal handgun training previously and neither had my friend whom I had shot with. I think had both shot rifle/shotgun before (don't remember). Nothing went full-auto on us. I (with my paper plate size groups low + left) was quite jealous of my friend's saucer size groups... at 7 yards
which were also low + left. Bless his soul. (he's still alive).
As far as formal safety training goes:
The NRA instructor was even more stringent about safety practices than I was. He removed all ammo from the room before dry fire practicing - which I wasn't doing at the time. He was very vigilant in watching our trigger finger discipline and muzzle direction and was set to alert us of any dangerous habits. I recommend the NRA first steps course - I thought it was great. I don't know what's available in your area but we had a variety of firearms to choose from and practice familiarity with, did dry-fire practice with/without lasers, dry fired and live fired on the range. Learned a couple stances, and I could go on...
Looking back at myself when I first started, I knew and followed the safety rules but slowly acquired how it would look like applied to situations as they came up (or when I saw others' failures). I'd like to hopefully shorten that time for you on just 1 point: (forgive me if you know this already, I don't know if you have many shooting buddies to learn from)
Keeping the gun pointed in a safe direction:
When something goes wrong with the gun (squib load, failure to fire/feed/eject) a common pitfall is that the shooter will turn to the buddy/instructor with their attention focused on the malfunctioning gun which is typically held about chest height...which points wherever they turn. So everyone down the line has been muzzle swept and their buddy is looking down the barrel. (and sometimes a finger is still on the trigger). You may have the privilege of witnessing /experiencing this so watch out. watch for this when you or your wife practice - it's easier to be complacent in the comfort of home. You can turn the head and even the torso if you must as long as the arm/firearm is still pointed in a safe direction (and finger off the trigger). Now what about if you're pointing North, and need to point South, but someone is to the East/West? You could point at the ground (watch for feet/toes) as you turn and then bring it back up when you're looking at the destination. Or you could point up at the sky (I usually don't do that) but the gun should be raised above your head in that case (just bending the elbow would put the muzzle about chin height)
And you'll see this one a lot on Youtube firearm review videos: as much as possible even if you "know" the gun is unloaded avoid putting a hand in front of the muzzle. Unless it is field stripped/disassembled, it's not a good thing to do nor a good habit to form. And be careful of those youtube videos. I've seen some unsafe practices demonstrated, and it seems just about everyone is trying to give instruction. (apparently, me included. that's my cue to quit