Manifest Destiny
by Kegler

Six answers are modified before entry, as explained by 30 Across (the results will not be words).  17A is a variant spelling.

Manifest Destiny grid

Across
1Litigants holding power mostly settled with partner very quickly (14)
10Eggs found in Puerto Vallarta (3)
12Return pale yellow unfinished pots (5)
13Wait for wedding participant, losing hour, ultimately (4)
15Rebuke soldier guarding criminal mob; brilliant (10)
16And others, running behind, returned (2,2)
17Half afraid it's an evil demon (5)
20Consumed meat spread after start of party (3)
22Youngster Gram nearly dropped into trench (3,3)
23Discussed, 'kay, slow marching beat (7)
25Make things too easy for evil spy; I'm distraught (12)
28Rags Bill with a couple of loathsome names (8)
30See instructions
34Fish unsatisfactory in one pasta dish (8)
39One who overcame negative question upset auditors (12)
40Nothing strange in happy greeting (4,3)
42One endless task for newsman (6)
43English nobleman losing lady's attention (3)
45Yes, we are keeping promise (5)
46Pace wildly in flowing garment (4)
47Somehow end up at HP, capturing page with digitally-controlled image? (4,6)
50Financial support about runs dry (4)
51Separates saline drops? (5)
52Take advantage of Sue, sadly (3)
53Ought to tolerate essentially British women having no interest in bones (8,6)
Down
1Thought-provoking ballad about one Confederate soldier returning (8)
2New York supports a “No” vote (3)
3Dye plant's second offense reduced (7)
4Quiet churchgoers cut short braid of hair (5)
5Hotel manager presents tree (3)
6Terrible snit fails to be... (4)
7...referenced or witnessed at hearing (5)
8Illuminated every repetitive chant (6)
9Perhaps young dogs mauled Presley (7)
11Restlessly move around, returning mid-July with book (6)
14Embraced by Quayle and Koch, Conservative is twisted, perhaps? (6)
18“Party of Five” hosted by actress Charlotte (4)
19Disheveled, ratty, like a prostitute (5)
21Make clear animal consumes last half of beef (5)
24Set of pictures of one large sponge (5)
26Camera shot includes white chess piece (4)
27Ancient city featured in handout I carry (5)
29Radio personality Don is embracing Greek character (4)
31Mild oath is, for example, strangely sad (5)
32Orville primarily signs comments from Wilbur, perhaps? (5)
33Tells of exceptionally rare ants (8)
34Reasonable soldier riding bus (7)
35I fly across blue line on a map (6)
36Leaders of Japan utter nonsense every month (4)
37Reportedly choose an entrance for bullfighter's assistant (7)
38Drinks head of beer, and sweats (6)
39Repositioned tripod is motionless (6)
41Profundity of certain baseball player cradling injured pet (5)
42Prize commercial describing fight (5)
44Vehicle bringing back residents of Tuamotu Archipelago (4)
48Laugh long with actor Holbrook (3)
49Lead-plated uranium bar (3)

Solution