The watch thing is a continuity error. Apparently he didn’t have it on in the flashforward scenes at the start of season 5 so they had to build in a plot mechanism to remove it so the pedants wouldn’t point it out.
An awesome finale. I watched it twice yesterday. The first time I picked up on a few subtle points but the second time revealed so much more. It couldn’t have ended any better. Despite hating Walt after he killed Mike, he redeemed himself fully at the end. Even the lyrics of Baby Blue were absolutely perfect…
Guess I got what I deserve
Kept you waiting there, too long my love
All that time, without a word
Didn’t know you’d think, that I’d forget, or I’d regret
The special love I have for you
My baby blue
That’ll surpass Don’t Stop Believin’ as the best final song ever.