The 80's thing aside, his choice of clothing made sense for a guy who thought he was cool, hip and a big shot. Funny character.
You want something corny? You got it!

I think that Grady was giving him a spot (a handicap, like the 7 and 8 out for example, meaning that if he makes the 7 or 8, then he wins the game), and when he says that to Grady ("up your a$$ with the spot"), that means that he no longer wants or needs the spot, and he will be playing Grady even up from then on. Great movie, but The Hustler was much better in my opinion.

and then Grady replys" "that's fine by me"
What do these lines mean?
"That is rather slippery of you agent Starling"

Hey Grady, up your a$$ with the spot. That OK with you?

For the love ofhe's wearing slacks and a dress shirt WTF. It's the Steve Martin look in "The Jerk"

his clothes were awesome. perfect attire picked for that scene. sleazy yet showy.

His lines were the best in the movie.

he looked like he's never paid his taxes.
A day without sunshine is like, you know, night.

Those were "suave" clothes for that time period, however, they weren't the trend.

"The impossible dream" is what he says.

"It's like a nightmare isnt it? It just keeps getting worse and worse doesnt it? Ooohh!! The American dream." He is the best.

I thought his performance was flawless and very entertaining. As for his pool playing, although a bit inconsistent over the years, Keith McCready is one of the most talented players to ever pick up a cue.

He wasnt a bad actor, I thought he was quite good and delivered his lined excellently.

His real name is Keith McCready. He was a mainstay on the pro pool circuit for quite a while, but now relegates his talent to trick-shot tournaments. Also known to be a notorious hustler in the 70's. Explains the bad acting, and, as you noted, attire.
"The key is, you've got to be crazy to maintain your sanity"