Don't you remember the song 'She's fresh' by Kool and the Gang in 1985?

On the first season DVD Bennie Richburg a writer talks about how he was hired to basically help write dialogue for the Will Smith character.
He was credited as "West Philly Homeboy Consultant" so a lot of the slang used was written by him.

I doubt Will Smith invented the majority of the slang words he used, except maybe "fresh", because I've never heard anybody else in real life being described as "fresh" besides the Fresh Prince himself.
But this show was pretty much the introduction to Black urban youth, hip hop, slang and culture for me.

By the time the show came out, all of those words were being used in the hip hop community.

Some of these words were in existence before 1990. Whether they were common is debatable.
"Homeboy" "Watch the bag homeboy" 1988 Eazy-E "Nomore Questions"
"Fly" "Flygirl" 80s rap song
"Dope" "Dope Beat" - KRS One (1987)
"Honey" is a hard one.
"Word up" probably came later. That's more new school East Coast slang.
I think "homeboy" is Southern in origin. Black and white Southerners say "boy" and "girl" a lot. And no white Southerners don't always mean it in a racist way. They just talk like that to youth, regardless of race.
Unrelated note, "B" (which is short for "brotha") is debatable. I never really heard many Northern blacks say it, despite what the movies might seem to show. That would be Southern blacks.

No way. Bob Marley released a song called "Jamming" in 1977, long before Will Smith started recording, and it's entirely likely the even he's not the first to use Jam/Jamming in reference to music.

The sun is shining but the ice is slippery.

Maybe the expression "jam".

I'm sure he's not the originator. Well-known rappers existed before 1990.

The sun is shining but the ice is slippery.