The first pair of answers was discussed in this blog just a couple of days ago. 1A and 1D: Maintain (avow) crosses with aver. Sometimes you just have to play with it to see which word will fit in which position.
5A and 5D: Fiddle with (amend), crossing with alter.
10A and 10D: Rubberneck (gawk) crosses with gape. One of my pet peeves is gapers' block...when traffic is stalled because of the number of people slowing down and/or stopping to gawk at an accidence scene.
25A and 25D: Pair (duo) and dyad. This was easier, since they didn't contain the same number of letters.
26A and 26D: Dodge (evade) and elude.
31A and 31D: Gusto (vim) and verve. Wanted vigor in the down position.
53A and 53D: It's all downhill from here (apogee) and acme. Apogee is definitely a cool word...acme reminds me of Roadrunner. Meep-meep.
57A and 57D: Tore (ruptured), crossing with rent...that sounds so biblical.
There were two very good long phrase answers...4D: They're unlikely to work (wild ideas) and 37D: Death jokes and such (dark humor). The second was a gimme, but I don't know why.
It's an amazing feat of construction when the non-theme fill isn't compromised in order to pull off the theme. That's the case here.
14A: Part of Caesar's boast (vidi). Good one.
20A: Motor Trend job (road test).
29A: Start of a phrase meaning "always" (day in). I can't believe that one took so long to get.
36A: Annual parade site (Pasadena).
42A: N.F.L. coach who was undefeated in 1972 (Don Shula). My dad was a big Miami Dolphins fan. He lived in Colorado for a few years and proudly wore his Dolphins jacket. I always thought someone would jump him.
44A: Like tennis balls and dinners (served). This kind of clue usually makes me stop and think...they're rarely gimmes.
2D: In __ (form of research) (vivo). Is that Latin for in life?
I liked the tie-in 33D: Changers of 34A...giving us maids and linens. I was a hotel maid the summer before my senior year, at a nice hotel on Palm Beach. I made some pretty nice tips...just for changing linens.