ENRTE B757-200 IS IMPACTED BY WX; CAUSING AN ALTERNATE REROUTE; THEN REROUTE BACK TO IAD; ORIGINAL DEST. ATC INITIATED MAP RESULTS IN LOW FUEL EICAS ON LNDG. PIC QUESTIONS INTRA COMPANY COORD ALERTING DELAYS ABOUT IAD RWY CLOSURE.

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WITHOUT PRIOR WARNING; WE WERE ISSUED HOLDING OVER BVT AT FL370. ZAU ASKED FOR OUR ENDURANCE IN THE HOLD AND WE REPLIED IT WOULD BE ONLY 30 MINS; NOT THE 45 MINS UNTIL OUR EFC. HE THEN GAVE US DELAYING VECTORS AND REPLIED TO OUR QUERY OF HOW MUCH LONGER IT WOULD BE BY SAYING ZOB AND ZID WERE NOT GOING TO ACCEPT IAD BOUND TFC. DISPATCH SUGGESTED WE PROCEED TO MDT AND ATTEMPT TO REFILE TO IAD ONCE CLOSER. WE DECLARED MDT AS OUR DEST AND WITHOUT HAVING TO REQUEST IT; ATC GAVE US AN MDT CLRNC; FOLLOWED ALMOST IMMEDIATELY WITH A RECLRNC TO IAD. EVEN AFTER THE LONG DELAY ENRTE; PLANNED TOUCHDOWN FUEL AT IAD WAS 9.0 LBS (ORIGINAL FLT PLAN FUEL RELEASE 3 SHOWED LNDG WITH 13.0 LBS). POTOMAC APCH CONTINUED GIVING DELAYING VECTORS THROUGHOUT OUR APCH. WE WERE GIVEN 170 KIAS UNTIL THE MARKER OF RWY 19L. AT SOME POINT; SOMEONE ON THE APCH FREQ ASKED WHY THEY WERE ONLY SHOOTING APCHS ON RWY 19L AND THE CTLR RESPONDED THAT THERE WAS A DISABLED ACFT ON RWY 19R. FLYING THE ASSIGNED SPD SEEMED TO PUT US TOO CLOSE TO THE TFC AHEAD; SO WE BEGAN TO SLOW AND THEN THE CTLR ASKED US TO GO TO TARGET SPD (WE WERE ALREADY APCHING THE SLOWEST POSSIBLE SPD). THE PREVIOUS TFC DISAPPEARED FROM OUR TCASII DISPLAY AND THE LCL CTLR ASKED IF WE HAD IT VISUALLY. WE COULD NOT SEE THE RWY OR TFC. TWR GAVE US A MISSED APCH CLRNC AND THE FO (PNF) ACCEPTED AND DECLARED MINIMUM FUEL PER OUR PREVIOUS DECISION. APCH WAS ALSO INFORMED OF OUR FUEL AND WE WERE VECTORED TO COME IN ON THE APCH AFTER ALL OTHER TFC. WE WERE DISCUSSING FORCING THE CTLR'S TURN ONTO FINAL AS HE TURNED US IN. THIS TIME; A DIFFERENT LCL CTLR CLRED US TO LAND AND WE SPECIFICALLY REQUESTED TO CONFIRM ADEQUATE SPACING ON THE TFC AHEAD. ATC CONFIRMED HE HAD SPACING AND THEN PROCEEDED TO CLR A DC9 ONTO THE RWY FOR TKOF WHEN WE WERE INSIDE A 2 MI FINAL. WE TOUCHED DOWN AND AFTER GOING TO IDLE REVERSE; GOT A LOW FUEL EICAS. WE BLOCKED WITH 4.3 LBS AFTER INITIATING THE MISS AT ALMOST 7.0 LBS ON THE FUEL. DISPATCH HAD NOT BEEN INFORMED OF THE DISABLED ACFT ON RWY 19R; NOR HAD WE; NOR HAD OUR ATC COORDINATORS AT ORD. WHY?