(Insert usual caveats about attempts to search for the answer here.)

Had some weather-related delays and missed connections on Friday and was puzzled by the various responses by UA's computer system to my situation. All was, of course, resolved as soon as I spoke to a human being but I'm curious how the computer does its magic and wondering if there's anything I can proactively do in the future to make the computer treat me as nicely as a human.

Here's the story in a nutshell:

• Booked HSV-IAH-LAS with a 90 minute layover departing 1:11pm.
• About 3 hours pre departure, notified of a 65 minute delay on HSV-IAH.
• On checking my reservation found two paths home booked: my original flights plus flights HAV-CLT-LAS on US with similar "original" departure times (1:06) and arrival in LAS but avoiding the weather in IAH.
• Called a UA agent for clarification. Apparently the system predicted I would misconnect in IAH and I had the option to fly the US legs even though they left before my "predicted" misconnect. Given a cleared UG on my planed flight, 2 later IAH-LAS options that day with plenty of E+ seats, plus 3 additional ways to get home via LAX or SFO, I elected to take my chances in IAH and stay on UA metal.
• Flight departs at predicted delayed time but circles IAH in the air a lot longer. I end up misconnecting by 3 minutes. Meanwhile UA had auto-rebooked me on a flight the next morning, with a confirmed UG.
• GA at the flight I had just missed tried to rebook me on one of the earlier departures that evening but couldn't on any of them. Put me standby on the next one (7:30).
• I went directly to the UA club and politely explained my situation there. I got an immediate exit row seat on the 9pm, stayed standby on 7:30, and the agent said she'd keep refreshing the screen. 10 minutes later she found me and handed me an exit row seat on the 7:30. I got home only about 3 hours late.

Questions:
- The proactive reroute on US looks (in hindsight) like it would have been my best option, avoiding the IAH weather delays. But I'd never been offered a reroute in advance of a flight (that still had a fighting chance according to flight times) before and didn't feel like experimenting (or skipping E+). Is this common and usually a good idea?
- When the automated UA system rebooks, does it just take a snapshot at that instant and give you the best choice? By the time I talked to a person there were tons of seats on the 9pm, but it's possible they were all "blocked" protecting other passengers at the instant the system tried to rebook me.
- Does the automated system try to preserve your upgrade? I obviously preferred going home that evening in an exit row to spending the night and flying in a bigger seat in the morning... I would hope the system would know that as well.
- Did the United Club agent have access to more reroute options than the Gate Agent? Or just more time/inclination to help? Or just luck of the draw on timing on the 9pm flight seats (wide open in the 5 minutes it took to walk from the gate to the club).
- Is there anything one can do to "force" the system to look for better seats more often? Would you have done any differently than me and why?