First, guns don't protect, never have, never will.
The first eight of your 457 word wall of text shows you're so out of touch with reality that there's no point in reading the rest.
The primary function of guns in private hands is to protect those who carry them. They do that exceptionally well. In criminal attacks, resistance with gun is the most effective way to avoid injury or death. It's substantially more effective than the second best - knuckling under completely - and beats the pants off everything else, from running away, to trying to talk your way out, to resisting with bare hands or other tools. (Resisting with knife is about the worst.)
Research on self-defense is hard, because faiures leave tracks in crime stats while successes usually don't (and often leave the self-defended victim with an incentive to keep quiet about it). Nevertheless, even the first well-run projects were able to put a lower bound of guns preventing or aborting more than six times as many crimes as they aid in committing.
In private hands they're safer than police, too. A defense-with-gun is usually effected by no more than brandishing or occasionally getting off a round in the general direction of the perp. But of those instances where a victim or a policeman shoots someone believed to be a perpetrator, the cop is over 5 1/2 times as likely to erroneously shoot an innocent than an armed private citizen.
My family has substantial personal experience with armed self defense. For just a few examples on my wife's side: In college she was accosted by the rapist in the window, who was dressed in just running shoes and a dirty knife. Fortunately there was a hunting rifle behind the bed: She actually had to go as far as cocking it before he stopped trying to get her to drop it and jumped back out the window - apparently to take it out on another girl a few blocks away, with over 130 cuts while raping her. Her mother defended self and family against a Klan attack with a pistol. (Her granddad was caught away from his gun, though, and had to do his anti-Klan defense with a hammer.) Then there was the aunt, the uncle, ...
At the larger scale it's hard to argue with the fact that the US, founded in a revolution (by religious nut with guns) against their self-admitted "legitimate government" and with over half the adult civilian population armed, has now gone over two centuries without a substantial attack from abroad and only one major internal war, while Europe continues to suffer from genocidal wars, often with multi-million body counts. (With the exception of Switzerland, of course: Every adult citizen there is armed and has had military training. Even World Wars go around them.)
It's also hard to argue with the fact that the US is multi-ethnic, and the common denominator of each of its ethnic groups is that their members' murder victimization rate is substantially less than that of contemporary members of the same ethnic group still residing in their land of origin.
As for resisting an oppressive regime if push comes to shove: We have experiences like "The Battle of Athens" just after WWII, and the documented question from Nixon to a thnk-tank about what would happen if he suspended the presidential election. (Answer: That would precipitate an armed rebellion, and the population was well enough armed that it would succeed.) Uprisings aren't always successful and small or UNarmed uprisings are often put down, sometimes with lots of deaths. (Witness the Bonus Marchers' Massacre.) But recent decades of world politics have shown how effective a popular uprising can be, against even a coalition of world powers and superpowers.
If it came to that in the US, you can expect a substantial amount of the military (especially retirees) to be on the side of the people, along with lots of military equipment raided from armories. (You can see that now in the Middle East. The big difference between Al Queda and ISIS/ISIL is that the latter has bunch of colonels and other line officers, force-retired and blocked from normal politics in the wake of the 2003 invasion of Iraq and overthrow of the Ba'athists - along with a lot of seized military arms. The former is a bunch of terrorists, the latter has a substantial army.