At what point are you getting the error message?
After the final booking page after I click "book".
If I book EK F With Alaska points to Amman, but the first leg to DXB is only available in J, DXB to Amman is F. If F availability frees up before my flight, do I get to upgrade free to F?
What do you mean by "free", without any miles?
Yes because I'm paying full amount.
I would think so. Why don't you book it all in J and pay J. If F opens, then switch.
Is Emirates known to release F award availability closer to a flight? Flight is in early February, 9/14 seats are empty
Yes.
And if booked with J and then F opens you just pay the difference in miles to upgrade?
Similar to plan b with United
Bah!
I'm going to assume that is a bad "Bah" and not a "Bah" that you could care less.
Bah is always bad. Meh is always I couldn't care less.