Hi Boomer. I'm a veteran also. Three years in the Army. However, being an ordinary grunt, my training and experience never included sidearms. M-16, M-79 grenade launcher. That was it. So when I decided to get a pistol for home defense and then concealed carry, I started with a one hour (actually 45 minutes) one on one handgun lesson. It cost me $50 and was the best $50 I've spent in the last 12 years on firearms. If you can find something similar where you are, I think you'll get a lot of questions answered, start without self-taught bad habits, and most likely be on the way to your next handgun. I was. Do it with an open mind and no "I'm a veteran. I know what I'm doing" attitude, and you'll get a lot out of it.
When I sold a gun to a friend a few years ago, I offered to split the cost of a similar lesson with him. He had experience with rifles and hunting but not with handguns. He has thanked me for that at least ten times since then and offers that same advice at every opportunity.
I've had an XD9SC and still have an XDM-45 4.5". This is an excellent line of handguns. Heavier and "chunkier" than Glock but with enhanced safety features that are worth the extra ounces. One thing I can tell you about the line is that you'll find stiffer than average recoil springs. That protects the frame from being beat up by the slide. It also applies pressure to hold the side open against the lock. A small 45 is going to have an extra strong spring, making it seem all that much harder to release.
Personally, I almost never release the slide with the slide lock, preferring the sling shot method. Insert a loaded mag (please buy some snap caps--aka dummy rounds--for practice), then, with the gun pointed downrange, pull back on the rear slide serrations and release the slide. Be sure not to "ride" the slide, as you may reduce the force enough that it doesn't go into battery. Other people prefer to use the slide lock.
Slide locked open. A semi auto is designed to lock the slide open after firing the last round. The empty mag is part of the mechanism that does that. If the slide locks back without a magazine inserted or you pressing up on the slide lock, the gun is broken. Call the manufacturer. Springfield Armory has some of the best customer service there is.
But please, park any macho macho man notions out back and call a gun range that has instruction. You and your wife can even do it together, and then you'll see most likely why most instructors say women make the best gun students...and often the best shooters, too. And also, please do yourself a favor, and don't take a file, sandpaper, or grinding compound to any of the working parts of your handgun, at least until you have mastered its use as is, and maybe not even then. Get hold of a couple of Massad Ayoob's books before you consider any mods.