George never thanks the town for helping him out with the money in the end. This might seem kind of rude, but it makes sense because George is so used to doing things for other people that he simply doesn't know how to react when someone does something for him. This is also illustrated during his "honeymoon" with Mary.
It comes across as his being so stunned he couldn't speak.
Also, it's not that his friends and family are doing a favor for him. They're thanking him for the many acts of kindness he's done for them all.
In the "I want to live again" scene, the snow doesn't begin to fall until George prays to God for his life back. That doubles as a Crowning Moment of Awesome for those who believe.
What's so bad about Pottersville anyway? Even more businesses seem to be booming. But, wait... In Pottersville, all the businesses in Bedford Falls went out of, well, business and were replaced with escapist entertainment — gambling, bars, and strip clubs — where people waste money and thus get deeper and deeper into the trouble that sends them there for escape in the first place. The nature of the businesses in Pottersville is a sign that the residents have given up and are simply trying to numb the pain of existing rather than trying to thrive and live.
When George finally snaps, take a look at the thing he destroys. It's a model of a suspension bridge, possibly built by George or one of his children as a hobby. Remember that George wanted to be an engineer or an architect when he was young, and that was just one of the many dreams he had to give up. But presumably he kept his love of engineering enough to build models in his spare time. And now that his life is starting to unravel, the first thing he sees is that model, that one pathetic reminder of his lost dreams of youth. No wonder that that model winds up taking the full brunt of his rage.
In-universe example: George is horrified by how much worse things would be for everyone he knows without him.
George helps a bunch of squatters skimp by on cheap housing instead of letting the supposed "villain" win. We even get a glimpse of what this would mean: a bustling nightlife strip that would undoubtedly boost the small town's economy.
...wow. I mean wow. You seem to have missed that the "bustling nightlife strip" was a street full of nightclubs and...shall we say houses of ill repute? That this is all controlled with an iron fist by the "supposed" villain who has a stranglehold over the entire town as he owns EVERYTHING in it? How about that the police are basically turned into a gang under the control of the "supposed" villain? Wow, a boost to the economy sounds worth it.
Not to mention that the town in that timeline didn't seem much wealthier than it did originally.
Part of the point of this movie is that money isn't everything, you know. Some things are more important—like integrity and charity (old-fashioned sense).
George provides cheap (but QUALITY) housing by sacrificing his own profits; Potter provides overpriced slums, but he was poor families' only option until George and the Building and Loan created a better alternative. In the Potterville Universe Potter's monopoly was complete - he owned all the businesses and the housing, so the lion's share of the wealth from the so-called "bustling" gin joints and strip clubs would have gone to Potter while the towns' actual citizens would continue to be bled dry and live in horrible conditions.
In the alternate reality, Martini is nowhere to be found, without explanation. Was he the child that was accidentally poisoned by the druggist?
The alternate Bedford Falls is shown to be a place that is much less safe and friendly than it is in George's reality. In George's world, Mary is an outgoing, happy woman. Even when George hid her bathrobe, her first reaction was outrage, not fear. Now consider how her Pottersville self acted - she walked hunched and clearly trying to avoid attention, and nearly had a nervous breakdown when George tried to talk to her. Sure a strange man running over and insisting you were his wife is going to freak most people out, but her overall demeanor is far more timid and fearful in general. What could have happened in this alternate timeline to make her like that?
Why is George allowing Uncle Billy to handle the money at all?
There's a difference between being forgetful and being irresponsible. Also, YOU come up with a way to tell an old man that he's not fit for the duties he's been performing all his life without a really solid reason.
That may be for the better, since Pottersville Mrs. Bailey mentions that after the Building and Loan went out of business, Uncle Billy was put in a mental hospital. Whether that's because he's too loopy to be out on his own or because he just didn't know what else to do with himself is probably up for debate.
I always imagined that Uncle Billy simply couldn't handle that his business went belly up, had a nervous breakdown, and was hauled off to the funny farm in a straight jacket.
The bar for commitment to a mental institution was a lot lower in the 1940's. For all we know (and it it's perfectly within character) Potter may have arranged for Uncle Billy to be committed so he could take over the Building and Loan. Having sometimes perfectly fine people committed was a common underhanded way for someone to get his hands on a business or estate. As it was, this was an era when homosexuals and people with learning disabilities could be confined to a mental institution in most jurisdictions. All it takes is one crooked judge...and psychiatry being what it was back then it would be next to impossible to convince the doctors to let you back out. Even if they did, the damage is already done.
Why does Mary need glasses in the Pottersville segment? Did George's existence somehow improve her eyesight?
She's working at the library now. Everyone knows that dames can't handle that much readin'. They'll go blind.
It's because George was the only man she ever loved. In this universe because George never existed and she is living in a Crapsack World , the men in that world would have been just as bad for her. A person of George's quality wouldn't exist. So she rather take her chances of being an old maid than to be a depressed wife.
She's living in one of the crappy little shacks Potter provides to working-class people and thus doesn't have adequate lighting at night, causing her to strain her eyes.