WDB TOO HEAVY; COULD NOT MAINTAIN ASSIGNED ALT.

Narrative

WE WERE FLT PLANNED TO CLB (INITIAL CRUISE LEVEL) TO FL330. REQUESTED FL330 FROM TYO ATC. WERE ADVISED FL310 AND FL330 WOULD BE AVAILABLE ONLY AFTER 'EXTENSIVE DELAY' BUT FL290 AND FL350 AVAILABLE WITH NO DELAY. OUR S/O ADVISED US (CAPT AND F/O) THAT WE COULD ACCEPT FL350; SO WE NOTIFIED ATC WE WOULD ACCEPT FL350. DURING CLB WE WERE VECTORED EXTENSIVELY DUE TO OUR INABILITY TO REACH CRUISING ALT (FL350) WITHIN THE ATC RESTRICTIONS (FL350 BY 180 NM E OF CHOSI VOR). WE EVENTUALLY REACHED FL350; BUT AFTER LEVELING OFF CAPT STATED 'WE ARE LOSING AIRSPD; WE CAN'T MAINTAIN THIS ALT.' I HAD BEEN INVOLVED WITH PASSING ON ETA'S TO CENTER/DEP CTL AND HAD NOT NOTICED SPD OR PWR SETTINGS. I SAW THE AIRSPD DECAYING AND NOTIFIED DEP CTL THAT 'WE ARE UNABLE TO MAINTAIN FL350 AND MUST DSND.' THEY REPLIED THAT THE REQUEST FOR LOWER ALT WAS NOT APPROVED. I THEN TOLD THEM THAT WE COULD NOT MAINTAIN FL350 AND AT THAT TIME WERE DESCENDING AND REQUESTED FL290. THEY THEN VECTORED US AGAIN; PROBABLY CLR OF CONFLICTING TFC; DOWN TO FL290 AND CLRED US ON OUR ROUTING. WE LATER DISCOVERED THAT OUR S/O HAD USED THE WRONG CHART FOR CALCULATING OUR ALT CAPABILITY AND THAT WE HAD BEEN APPROX 27000# TOO HEAVY FOR FL350. WE WERE HELD TO FL290 FOR MOST OF FLT; DESPITE REPEATED REQUESTS FOR CLB OR ROUTE CHANGE. WE WERE UNABLE TO ACCEPT ONE RECLRNC TO SFO AND WENT TO HNL FOR A FUEL STOP.