Annual re-watch: questions and comments.

A few answers:

Mr. Potter would have had a horse and buggy instead of a car, because he's cheap, old-fashioned, and joyless. Why buy a fancy new-fangled car when he already had a buggy and the hay was cheaper than gasoline?

The "Great Depression" had highs and lows, the economic situation varied from glum to terrifying, until the WWII war economy changed everything, and from what I've read the absolute worst period of the depression was around 1930. It's why Hoover was voted out and Roosevelt was voted in, Hoover wanted to leave the recovery entirely up to "market forces", but Roosevelt wanted to actively tweak things, and when he did the situation because a bit less bleak for ordinary working schmoes.

As to being out of school at 18, it happened back then. Child labor was still legal until the 1930s, and lots and lots of kids left school at 12 or earlier to get jobs. High school was considered an expendable luxury and might not have been nationally standardized at that point, in the 1920s some schools might still have been graduating their students at 16 or 17. Some universities also gave degrees after 3 years.

It was possible for an attractive woman to end up a spinster in those days, if she turned down offers and discouraged interest, she'd be considered a worthless 'old maid" at 25. But of course I find that plotline completely unconvincing, it's supposed to tell the audience that she was meant only for George, but the fact is that if a small-town woman in those days didn't find a good prospective husband by her late teens, she'd either plan to settle for someone who wasn't a soulmate, or go to New York.

I would say all of your points are valid weaknesses but I do have responses to 3 of them.

I would say I also struggled with your point "Why are they singing Auld Lang Syne on Christmas Eve"
I always thought they did this for universality. The level of church attendance and Christian identity in the US was very strong in 1945-1946, almost universal but not 100%. Frank Capra himself was pretty strong Catholic. My guess "Auld Lang Syne" was chosen to bring in virtually everyone. But I agree it is awkward. I always associate the song with a bunch of drunks slurring the words in dissipated revelry.

"The scene from 1934 where Potter offers George a job. Potter says back during the Depression. The Depression was over in 1934?"
I don't see where you are getting 1934 from that scene. It occurs right after discussion of Harry Bailey shooting down enemy aircraft, protecting US warships in WWII so no earlier than 1942?

"How did Mary end up a spinster? She was attractive and popular with the guys - we can tell from the dance. She also has a college degree."
Where are you getting that?

"Why doesn't he have a car?"

The horse and buggy forces everybody to look at him. It forces the cars to slow down and make room for him. The horse and buggy enables him to control the road. It enables him to control how people are driving and where they are looking. In a horse and buggy he is the centre of attention, everybody has to slow down for him and make way for him. Like a King.

"Mr Gower was old in 1919 and looks exactly the same in 1945. No worse for the wear after 26 years."

At least half the human population fits this description. 45 has been the new 25 for 22+ years. Half the human populations looks 10-15+ years younger than their age

"Why are they singing Auld Lang Syne on Christmas Eve. Who does this?"

In addition to what calcaylor posted, the universality of the song, the lyrics match the situation, the town is saying farewell to another attempt by Potter to take over their bank and town, they are saying farewell and let's not think about times gone by and instead celebrate the future of our town

"The Depression was over in 1934?"

Already addressed by Otter

"How did George not manage to run into her in such a small town"

She went away to college

"How did Mary end up a spinster?"

There was only one man for her, George, and if he was never born, she would never marry, they were soul mates. She herself foreshadows her own Georgeless fate (rather be a spinster than marry somebody else):

George: Mary Hatch, why in the world did you ever marry a guy like me?
Mary: To keep from being an old maid.
George: You could have married Sam Wainwright, or anybody else in town.
Mary: I didn’t want anybody else in town. I want my baby to look like you.

"Was Uncle Billy an alcoholic"

Perhaps

"Mr Welch"

For the same reason George did not recognize Vi (the promiscuous classmate), their town was a small town but large enough for some people to not know eachother. In my own hood that I lived in for 30 years, most of the people did not and do know each other, neighbours never spoke to eachother (and still don't)

"If he just bought land he would have been wealthy."

He had no money nor did his family have money, and buying land does not magically make one wealthy

A fancy horse-led carriage is classier and more stately than a new fangled contraption. In those days, some carriages were very expensive with bragging rights which would be more elitist than a car that just anyone has.

First line explains the reason they're singing that song. Xmas/New Year's season so it's fine to sing.

Actor Charles Lane looked old and hadn't aged in decades. Coincidentally, he's in this movie.

Mary told George she would never have married anyone else. She loved him since they were children.
College degree in Liberal Arts which was popular at one time. That would allow her to become a librarian or teacher.

Uncle Billy wasn't an alcoholic. Bad memory or perhaps a bit dull.

No reason for Mr. Welch to know George. Only the teacher and mom Mary would know each other.

Mr Potter explained that George kept everything affordable for the townsfolk by charging loans at cost instead of profit. The houses on Bailey land were affordable for the same reason.