Perl, score: 2655 2630

#!perl -l
%p = qw{A 1 B 3 C 3 D 2 E 1 F 4 G 2 H 4 I 1 J 8 K 5 L 1 M 3 N 1 O 1 P 3 Q 10 R 1 S 1 T 1 U 1 V 4 W 4 X 8 Y 4 Z 10 x 0};
/[A-Z]+/,push @R,$& for <>;
@R = sort{length($b)<=>length($a)}@R;
for(@R) {push@W,$_;push@W,"$`x$'" while /./g;push@O,($_)x(1+length)}
$l = "AAAAAAAAABBCCDDDDEEEEEEEEEEEEFFGGGHHIIIIIIIIIJKLLLLMMNNNNNNOOOOOOOOPPQRRRRRRSSSSTTTTTTUUUUVVWWXYYZxx";
@S = map {$r='';for$x(A..Z,'x'){$r.="${x}{".(1*s/$x//g).",}"};"^$r\$"} map{"$_"}@W;
sub score{$r=0;$r+=$p{$_}for split'',$rr=pop;$r*length$rr}
@X = map{score$_}@W;
$f = 'x';
for(;;) {
$best = -1; $besti = 0;
for ($i=0;$i<@S;$i++) {
    next if $X[$i] < $best;
    if ($O[$i]!~/^[$f]/ && $l=~$S[$i]) {
    $best = $X[$i];
    $besti = $i;
    }
}
if($best < 0){
    $ls = score$l;
    print "left: $l (-$ls)";
    $tot -= $ls;
    print "total: $tot";
    exit;
}
$l=~s/$_// for $W[$besti]=~/./g;
$O[$besti]=~/./; $f .= $&;
print "$W[$besti]/$O[$besti] ($X[$besti])";
$tot += $X[$besti];
}

Use:

$ perl ./scrab.pl <~/sowpods.txt
OXYPHENBUTAZONE/OXYPHENBUTAZONE (615)
MICROEARTHQUAKE/MICROEARTHQUAKE (525)
NONOBJECTIVISMS/NONOBJECTIVISMS (465)
DAFFADOWNDILLY/DAFFADOWNDILLY (406)
PREINTERVIEWIxG/PREINTERVIEWING (345)
LITURGIOLOGxSTS/LITURGIOLOGISTS (240)
URDEE/URDEE (30)
EE/EE (4)
AA/AA (4)
left: AA (-4)
total: 2630

Use of blanks actually does not give that much while significantly slows down the execution:

$ perl ./scrab.pl <~/sowpods.txt 
OXYPHENBUTAZONE/OXYPHENBUTAZONE (615)
MICROEARTHQUAKE/MICROEARTHQUAKE (525)
NONOBJECTIVISMS/NONOBJECTIVISMS (465)
DAFFADOWNDILLY/DAFFADOWNDILLY (406)
PREINTERVIEWED/PREINTERVIEWED (322)
LITURGIOLOGISTS/LITURGIOLOGISTS (255)
RUGAE/RUGAE (30)
EE/EE (4)
AA/AA (4)
left: Axx (-3)
total: 2623

After adding some heuristics:

$ time perl ./scrab.pl <~/sowpods.txt 
OXYPHENBUTAZONE/OXYPHENBUTAZONE (615)
MICROEARTHQUAKE/MICROEARTHQUAKE (525)
NONOBJECTIVISMS/NONOBJECTIVISMS (465)
PREFIGURATIVELY/PREFIGURATIVELY (405)
DOWNREGULATIONS/DOWNREGULATIONS (300)
FORGEAxILITIES/FORGEABILITIES (238)
ADWAxDED/ADWARDED (104)
EA/EA (4)
left: L (-1)
total: 2655

real    3m58.517s
user    3m57.832s
sys 0m0.512s