FUEL DISTRIBUTION SYS ANOMALY AND DETERIORATING VISIBILITY COMBINE TO FORCE MD11 FLT CREW TO CONTINUE APCH AND LNDG DESPITE TECHNICAL FAILURE TO COMPLY WITH STABILIZED APCH CRITERIA ON FINAL.

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THE CAPT AND I RPTED IN ZZZ1 AFTER REDUCED REST DUE TO A LATE ARR THE DAY BEFORE. SCHEDULING REDUCED OUR PREFLT TIME FROM 1 HR TO 45 MINS TO TRY TO MINIMIZE THE DELAY. AFTER LOOKING AT THE FLT RELEASE WE DECIDED WE WANTED MORE FUEL THAN THE DISPATCHER HAD GIVEN US. THE CAPT EXPLAINED HIS REASONS TO THE DISPATCHER WHO BECAME DEFENSIVE AND TURNED THE REQUEST INTO AN ISSUE. DESPITE THIS; WE DID OUR BEST TO NOT RUSH OUR PREFLTS AND WERE VERY AWARE OF THE POTENTIAL FOR ERRORS. DURING THE DSCNT INTO ZZZ; AT APPROX 12000 FT WE RECEIVED 2 LEVEL 1 ALERTS: 'TNK 1 TIP FUEL TRAPPED' AND 'TANK 1 FUEL QUANTITY LOW.' 5700 LBS OF FUEL WAS TRAPPED IN THE TIP TANK OF TANK #1 LEAVING US WITH NOT MUCH MORE THAN EMER FUEL AVAILABLE. I WAS CERTAINLY GLAD THE CAPT PERSUADED THE DISPATCHER ABOUT THE ADDITIONAL FUEL AT THIS POINT. WHEN WE CHKED IN WITH ZZZ APCH I INFORMED THE CTLR THAT WE WOULD BE UNABLE TO ACCEPT A DELAY AS WE WERE HAVING TROUBLE WITH OUR FUEL SYS. HE VECTORED US FOR A STRAIGHT IN TO RWY 11 THINKING THAT THE WX WAS STILL VFR AS ADVERTISED ON THE ATIS. IN FACT THE WX HAD DETERIORATED TO MVFR. WHEN I ASKED IF WE WERE CLRED TO INTERCEPT THE LOC; HE REPLIED THAT HE WANTED US TO IDENT THE ARPT FOR THE VISUAL. I TOLD HIM THAT THE WX HAD CHANGED AND THAT WAS NOT POSSIBLE. BY THIS TIME WE WERE HIGH FOR THE APCH. WE FINALLY PICKED UP THE RWY VISUALLY; AND THE CAPT CORRECTED THE GLIDE PATH. EVEN THOUGH WE WERE HIGH ON THE GS AT 1000 FT WITH A SINK RATE OF ABOUT 1100 FPM; WE ELECTED TO CONTINUE THE APCH DUE TO THE UNCERTAINTY OF HOW MUCH FUEL WOULD BE AVAILABLE TO US FOR A GAR AND ANOTHER APCH. WE WERE STABLE BY 500 FT. EVEN THOUGH THERE IS A HUGE EMPHASIS ON BEING STABLE AT 1000 FT; WE FELT THIS WAS THE SAFEST COURSE OF ACTION DUE TO THE FUEL PROB. ON SHORT FINAL ON THE APCH THERE WAS ONLY 3000 LBS IN TANK #2; AND ONLY 3000 LBS THAT WE COULD GET TO IN TANK #1.