Sounds like you have a pretty good handle on things, and the answers thus far are accurate, so I'll just add my 2 cents on the routing. I've flown SFO-FRA quite a bunch, and also fly SFO-ORD very often.
Since they would need to be a separate res, give yourself plenty of time for the SFO connection (I would say min 2 hours). Once booked, you can call in and have UA put a note in the PNR's to "link" the reservations. This is just a fall back measure in case of some issue.
You won't likely be able to use the Polaris lounge in ORD since you won't be on the Polaris ticket yet. SFO polaris lounge isn't done yet, and the old UA first lounge in intl is a bit crowded these days. SFO is a fine airport to kill time though. Also give yourself plenty of time in FRA. I've had so many issues where I had to run through that airport my min connection time there is 3 hours these days. The Senator lounge is a fine place to relax, freshen up, and pass time.
It sounds like a lot more flying to get the upgrade to clear, but if that's the only way for the R fare it's not that bad. Plus you've have a nice ride over to FRA. Just some thoughts. Safe travels!