These are likely the Wilson Wu stories by Terry Bisson.
Here's an excerpt from "The Hole in the Hole", which is the story you remember about the passageway between a junkyard and the moon.
Everybody should have a friend like Wilson Wu, just to keep them guessing. Wu worked his way through high school as a pastry chef, then dropped out to form a rock band, then won a scholarship to Princeton (I think) for math (I think), then dropped out to get a job as an engineer, then made it halfway through medical school at night before becoming a lawyer, which is where I met him. He passed his bar exam on the first try. Somewhere along the line he decided he was gay, then decided he wasn’t (I don’t know what his wife thought of all this); he has been both democrat and republican, Catholic and Protestant, pro and anti gun-control. He can’t decide if he’s Chinese or American, or both.
As best I can tell, the narrator is named "Irving". "The Edge of the Universe", found in Numbers Don't Lie, is where the universe is beginning to contract.
Just then his friend Wilson, now working at the observatory on Muana Kea in Hawaii, calls him with news that they have discovered the edge of the universe. The universe, having expanded as far as it can, is beginning to contract. This will take millions of years; except, it seems, in some places isolated bubbles of time have begun to run backwards already.
Given two of the three stories are present, I'm suspecting your third might be "Get Me to the Church on Time", but the summary I found in the review is a bit disjointed:
I was not prepared for a Nobel-prize-winning scientist creating a bubble universe powered by a 1960s vintage black-and-white TV, a garden hose and a cell phone, while hiding in the Brooklyn tree house Irv and his neighbor built while they were kids. I wasn’t expecting weather-controlling moths and an ice sculpture of Traveler, Robert E Lee’s horse. I was not expecting a love letter to New York City, or the ending I got for Candy and Irv. I did not know what to expect when I bought Numbers Don’t Lie and it still all surprised me.
I can't claim any particular cleverness on this one. I just recognized the story about the junkyard and the one as one I'd answered before and then I trolled for other details.