Thanks everyone.

I called 1K desk and another agent switched me to 852 (w the change fee of course) and cleared all four right away. The amazing things is that I have UA 870 from SFO to JFK right after this and was also on waitlist list with NC0. She also cleared me for the second leg. So my cost is $1000 ($250*4) but confirmed upgrade for all 4 from NRT to JFK.

The $1000 could have been saved, though, if the first 1K agent I called was as helpful and knowledgeable as the last one.