How does JFK-BKK get to 50,000?

JFK-HEL-BKK-HEL-JFK is ~ 18,000 flown miles. Finnair Business Class gets a 100% cabin bonus when booked on a C or D fare. (Finnair Business Class booked on an I or R fare only gets a 25% cabin bonus.) And Platinum Pro gets an 80% bonus on base miles. So, 18,000 + 18,000 + 14,400 = 50,400.

I also value domestic upgrades on AA.

Don't count on getting upgrades on AA unless you have status with AA.

I'd prefer to stay with AA, but the 30-segments to unlock Loyalty Rewards just isn't going to happen.

Fair enough, but will you get additional benefits by attaining oneworld Emerald status in a different program? If not, you're giving up potential domestic upgrades on AA for what? Admirals Club access on domestic AA flights is all that comes to mind. And you also have to consider how the value proposition from redeeming, say, IB Avios compares to redeeming AAdvantage miles.

Query: If I have IB Emerald status, can I reserve exit row seats on AA without charge?

Both IB Emerald and IB Sapphire get free MCE at time of booking. IB Ruby gets free MCE 24 hours before departure time.

Edited to add: If you opt to pursue oneworld status with AS, AS flies from LAS to three international gateways: LAX, SFO, and SEA. And flights on SQ also earn miles -- including elite-qualifying miles -- on AS.