I'm also a wide guy and feel the same about squeezing into 17" x 29" coach seats. Possible, but no joy. When I was EXP on American I still found that upgrades were hard to score; SEA is not an important AA city, and there were too many business travelers whose companies would happily shell out for them to buy FC, so upgrade seats were generally unavailable, and not available at all during the summer when tourist pressures make SEA unobtainable using most FF programs.

In your case I'd probably do some benefit/cost modeling using some of these factors as inputs:

Lurk on the "premium fare deals" board - https://www.flyertalk.com/forum/premium-fare-deals-740/ - which often has terrific leads on "cheap" seats up front.

Look for mileage sales. I don't know about Delta, but American has periodic sales for FF miles where you can come away under 2c/mile. AA charges 115K miles for a RT in business class to Europe, so at 2c that's $2300, which is not extraordinary but can be a good deal.

I've been a big fan of RTW tickets as a means of riding up front and saving money in the process. Oneworld's Oneworld Explorer product allows 16 flights over the space of a year, six of which can be in North America (including Central America and the Caribbean). The price of a 3-continent business class OWE started in Japan is $5990, and could give you something like this as an imaginary plan for a year - NRT-HKG-BOS-LAX-DFW-BOS-ORD-SFO-DFW-LHR-MAD-TLV-MAD-HEL-HKG-BKK-NRT

You'd still have several grand in your budget for short-haul travel, and with 40K miles up front you'd achieve elite status in AA (or BA, which would also get you lounge access in the US which AA elites don't). A big RTW every other year could help you maintain status in the off-year, and probably save money overall. Just a thought, anyway.