Chris,
Sorry to hear of your troubles with the Colt. I agree with finding a good gunsmith. EVERYONE needs a good gunsmith. I also 100% concur with the shock buff and heavier spring idea. As far as not being made for heavy loads....well, that's not entirely correct. It might be better said that it's not properly "configured" for heavier loads? As far as the frame, action, slide, etc....generally there is no difference in strength from any other Colt produced during the same timeframe.
The parts you have listed that have failed are all on the 1911 "prone to failure" list anyway -- along with the safety plunger housing, firing pin stop, ejector, and extractor. Depending on the date of manufacture for your pistol, the thumb safety may have been an MIM (Metal Injection Molded) part, and possibly the slide stop also. Just about ALL the big production 1911 makers have started using the MIM process. They say that it creates a more precise part and is cheaper to make, but they don't talk about the sacrifices in durability and strength. Typical marketing genius' assuming we are all stupid. Nothing comes for free with a 1911. Anyway, these are both parts that, as you know, are easily changed out with say, "Wilson" "Bullet Proof" parts.
I've learned that the first thing to do with a 1911 is find the heaviest spring it will handle (for my load of choice) without malfunctioning and then start using the shock buffs. The shock buffs also double as the perfect indicator for determining whether or not one's recoil spring is too light, or worn out. If the "buff" is banged to hell before 1000 rounds have been fired, then it's time for a new spring. The idea here is to tune the pistol to YOUR load of choice.
Was your heavier spring fixed rate, or variable? It can make all the difference in the world with a persnickity 1911. If it was fixed rate, then go with a variable rate one. It doesn't cost you much to try that. You've got a better chance of using a more powerful spring this way without any problems. For example, my Kimber Gold Match uses the 21.5 lb variable from Wolff while shooting my 200g LSWC over 4.5g of Bullseye.
Colts indeed made some poor 1911's for awhile - especially when you consider what they charged for them, but nowadays they aren't quite as bad as they were, say, 10 years ago -- that is, if you can live with the quarter pound extra of trigger pull that a "series 80" model will give you over any "series 70" design. I am fond of saying, "When you pay the extra for a 'series 80.' that is exactly what you get, 'extra.' If I had a series 80, like you, I'd start looking at my options for disabling the "Swartz Safety" stuff. "Poor," in the case of 1911s, is a relative statement though. In my opinion, just about all the major companies are making "poor" 1911s today, but again, that's from MY perspective, and I compare them all.
I am a person who WILL use a shock-buff in a self-defense pistol, BUT you've also gotta know that I am a cleaning & maintenance nut. I am also someone who has never had a shock buff fall apart on me in 20+ years of using them in IPSC matches and the like.
Now why would Colt want you to use an 8 round mag with hardball? I have my theory on this, but was wondering if you've considered the reason for it?
I wouldn't give up on your Colt just yet though. Most probably, you can correct ALL your problems and live happily ever after with it without spending too much more money. If not, then just sell it, and buy another brand. Wilson, Les Baer, Kimber are all good choices at the time of this post. People are starting to experience issues with the Springfields now also, but I won't elaborate to preclude a flame war. Sometimes, it's better to just buy a $500 1911, send it off to a "good" pistolsmith, and live happily ever after.
