While I sometimes do carry a "truck gun", the OP made several valid points. Like every single other consideration when talking firearms, tactics and techniques, you need to weigh the pros and the cons and make a choice based on what is most important to YOU. Everyone looks at things a little differently, and has different sets of life experiences and training, so not everyone will come to the same conclusion. Doesn't make them right or wrong, just......different.
There are a few things that I do consider wrong. Towards the top of the list is that if you carry a firearm, regardless of capacity, you need to carry at least 1 spare reload for that weapon. Statistically, if you're involved in a gunfight with a single assailant, you will fire every single round that was in your handgun. What if, like happens in the majority of the situations, there are 2 assailants? Whatcha gonna fight him with? After being in a fight for your life, how comfortable are you waiting for LE to arrive, while you sit there with any empty gun?
Never heard a valid argument for refusing to carry a reload. Most folks just don't wanna bother with additional weight/gear. That's just laziness and shows that your decision to carry a firearm for self-defense is either just window dressing, or delusional.
In Georgia, the defense for using deadly force is, paraphrased, "in defense of your life or to prevent serious bodily injury to yourself, OR TO PREVENT DEATH OR SERIOUS BODILY INJURY TO ANOTHER". So, once you have left the scene, it can be argued that you are no longer in danger, but you can easily argue that you are assisting the innocents still on the scene, to prevent their death or serious bodily injury.
This ain't Massachusetts. In Georgia you do not have an obligation to flee danger and leave the bad guy to his nefarious works. You can be the Good Samaritan and attempt to "save the day".
Amongst the many courses is teach is one I wrote specifically for civilians; Residential Room Clearing & Response to Active Shooter. All these considerations, and much more, are covered in depth and in detail.
I am still actively employed as a LEO and have been a LEO, either local or Federal, for over 20 years now. Large portion of that as an Instructor and SWAT member.
If you choose to carry any sort of firearm in your vehicle, it needs to be securely stowed, not just locked inside. Amazing what you can do with a heavy chain, a stout padlock, and a sturdy seat bracket.