SFN and dealing with a 14 hour flight, Anyone have experience?

I decide I can do it if I buy premium class middle aisle so I can get up and walk around and if I need to take a sleeping pill (34 hour flight) I can do so with people going on the other side.

Do they allow 65 and over emergency rows?

I used to get them often. When I started arriving with a cane and later a wheel chair, even though I walked onto the plane they stopped letting me. I know they expect the people in that aisle to help get people out the door so I assume no. but ask. I assume most good travel agents know the answer to that

You lift your heel off the ground, bend your ankle, pointing toes to your chin, then stretch foot out, pointing toes like a “ballerina”, then back and forth for a count of 20. Do a few sets every half hour or so.
By the end of the day, my neuropathy leg ankle is swollen a bit, so I do them in my Lazy-Boy during the commercials. Learned them at PT

When I fly to Los Angeles, CA twice a year, l always ask for and sit in bulk head seating. Bulkhead seating has extra leg room and lets me put my feet up on my backpack so that they are elevated. I also get up every 1/2 hr and walk down the aisle to the back of the plane and back twice to keep the blood flowing. This helps me get through my flight. I also wear compression socks to keep my legs from swelling.

I advise some stretching exercises but you really don't have room. Maybe use a bathroom stop for that too.