Thanks for the trip report and photos.
I love that area, and remember those switchbacks all too well! Your post put me right back on the trail.
(If you search for "2 weeks on the continental divide", that was my trip report, it's under a different user name because I let my membership lapse then renewed with a slightly different user name...).
I experienced altitude sickness this summer too, although perhaps not as severe as yours. Before the hike, I slept for 2 nights at 8,000 feet. The first day of the trip I hiked pretty hard up to 11,000 ft, where I camped (in the Lizard Head Wilderness, Colorado). I had been fine all day but that evening was totally lethargic, headachy, and couldn't keep any food down. I actually lied in my tent and watched a marmot (that had been nosing around camp all evening) sit on a log and chew the strap off my trekking pole--because I was too beat to get up and do anything about it! It was bad for me, and the marmot:
Anyway, lesson for me is to always sleep at altitude for THREE nights, without strenuous activity, prior to any big trip in the mountains.
BTW, I was fine the next day.