Traditionally, it's been the West Coast US gateways esp LAX that tends to have less expensive TPAC flights, but that doesn't seem to necessarily hold true anymore. Unfortunately, you are travelling at the worst possible time (except maybe Christmas holidays), summer flights are very busy in both directions across the big water. And flights from anywhere in North America to anywhere in Asia seem much higher than normal even now when we're not in high season. If you can get from Florida (or the East Coast) to Shanghai for $1100, I strongly suggest you consider doing that even if it means a Moscow connection. If you're flying Aeroflot, their international flights are now considered no worse than flying the longhaul USA carriers. The unattractiveness of a Moscow connection may end up being worth sucking it up to save a few hundred dollars.

Do you have any flexibility, especially on the return date? Even delaying until after Sept 1 can drop that fare down. August is notoriously awful for TPAC prices.

Try other major US cities, if a Florida origin is proving to be very expensive. You'd still have to find a way to get a cheap ticket to your US international gateway, but in the USA, at least there are options and specials. If you can snag something less expensive to anywhere in China (PEK, CAN) then it's relatively easy to get a domestic Chinese ticket or even use the train services. For domestic Chinese tickets, use www.ctrip.com or www.elong.com or www.travelzen.com all of which have English language versions of websites. Note: do not use these for international flights to China, and usually not for internationals out of China.

As for what's the best strategy for a very tall person travelling in Y, it to some extent depends on aircraft. At a minimum, get an aisle seat. It may be possible to snag an exit row but if you don't have frequent flyer status, very tough on a US carrier longhaul. Many airlines will not issue exit row assignments until check-in, so sometimes not doing online advance check in and showing up very early at the airport can produce one of these. Bulkhead seats get mixed reviews since some of them don't always have the leg room you expect, and you usually get babies and small kids around you.