The way I look at the spring issue is that if you're worried about the springs wearing out from the magazines being left loaded, just replace the springs periodically. Replacement magazine springs are very inexpensive ($17.29 for a package of three from Wolff Gunsprings) and are good preventative maintenance. Personally, if I were to keep a semi-auto magazine loaded all the time (I don't because my home defense handguns are revolvers) I'd simply replace the magazine springs annually and not worry about spring fatigue.
http://www.gunsprings.com/Semi-Auto%20Pistols/COLT/1911%20GOV'T%20PISTOL/cID1/mID1/dID1#805
That being said, you still need to have at least two magazines. This is because one of the most common causes for jams in a semi-automatic is problems with the magazine. If your gun jams while someone's trying to kick in your door in the middle of the night, you're not going to have time to fiddle with a magazine, it's much faster and more efficient to just drop the bum mag and insert a fresh one.
As for ammunition, I also recommend factory JHP ammo. The use of handloads presents several possible legal issues not the least of which is the potential for discrepancies in forensic examination of gunshot residue. If, for example, your handloads are loaded in Winchester cases, the police might compare the GSR from the shooting from that left by factory ammo. If your handloads leave less GSR at the distance you say you shot your attacker from than factory ammo does from the same distance, the cops may believe that you shot from a greater distance thus calling your entire story into question.
One of the nice things about the .45 ACP cartridge is that there are very few "bad" JHP loadings for it. Pick a 200-230gr JHP from a major ammo maker like Winchester, Remington, Federal, Hornady, Speer, or Cor-Bon, shoot at least 100 rounds of it to make sure it functions reliably in your gun, and then use the handloads for practice.
As far as the legal and psychological ramifications of shooting in self-defense, both Frank Ettin and Glenn E. Meyer are far more knowledgeable about such things than I (law and psychology are their respective professions) so I'll defer to them on such matters. My only advice on the matter is that in most of the U.S., the legal threshold for deadly force is the reasonable fear of imminent death or great bodily injury to yourself or another present innocent person. If you have any alternative to deadly force that does not place life and limb in equal or greater danger, it's always best to take said alternative.