As far as the name goes, I have more trouble believing he got the name
from the Black Panther organization and/or it's predecessor.
That has become quite obvious, friend Kip

One, it is believed that Marvel, maybe even Stan, changed Kirby's mask to cover up
all the Black skin because of how it might effect sales in the South.
"Believed" by yourself and by who else? It was clear from the beginning that the Black Panther was to be Marvel Comics' first black superhero. He was a young African man, a young
black African man. I don't see how this information could have escaped the dedicated white Marvel Comic's fan who happened to live deep in the racially-segregated South. What?...covering T'Challa's face and body with an all-concealing mask and costume is going to magically transform his flesh from black to white? Also, Avengers #52 - the Black Panther's first appearance as an Avenger in an Avengers comicbook - features him wearing his HALF MASK and TOTALLY UNMASKED in the story. Any reader of that comicbook would be made immediately and unmistakably aware that the Black Panther was a BLACK MAN.
Do we really think they'd risk Southern stores refusing to sell a title that plays homage to the Black Panther organization?
Look at the evidence and decide for yourself, Kip. I'm assuming that there were white youth living in the racially-segregated South who were likely fans of Marvel Comics' Avengers title back then. Read my previous post in this discussion. Read the dialogue. Read for yourself how the Black Panther of Wakanda in effect, becomes the incarnation of the Black Panther Party in that Avengers comicbook. T'Challa referred to black Americans being beaten and killed by racist whites - the same type of white person usually found living in the racially-segregated U.S. - as HIS people. They weren't Wakandans, Kip. T'Challa referred to black Americans as HIS people. T'Challa demanded that the Avengers allow him to take the Serpents down..."ALONE!" as he saw it as his right as a black man...as THE BLACK PANTHER to avenge the acts of violence those white racists committed against HIS people. The evidence is clear and irrefutable, Kip. In that moment, T'Challa became the incarnation of the Black Panther Party. How can you NOT see that?
Especially when they shortly thereafter dropped the word "Black" from his name to avoid any confusion.
In Avengers #52, it does appear that T'Challa is referred to and also refers to himself as simply "the Panther". However, as early as Avengers #54, T'Challa refers to himself as "the BLACK PANTHER" when engaging in superhero/supervillian banter with the villian Whirlwind. By issue #56, T'Challa says the following; "That will hardly be necessary, Archer! Or have you forgotten why I am called...the
BLACK PANTHER?" Later, speaking of avoiding confusion, T'Challa did undergo another name change, but it wasn't the "Black" that was dropped from his name, it was the "Panther". For a short time, the Black Panther was called the Black Leopard.
In Avengers #105, T'Challa explains to the nosy Hawkeye (resplendent in his powder-blue mini-dress with matching headband, the costume he chose to flit around in at that time, possibly in hopes of wooing the Scarlet Witch away from the Vision), why he changed his name. T'Challa says; "I did not want my personal goals and tribal heritage confused with political plans made by others. But in the final analysis, I decided that made as much sense as altering the Scarlet Witch's name--because witches are generally thought of as ugly. I am not a stereotype. I am myself. And I am the
BLACK PANTHER." Perhaps, after the events of Avengers #73 & #74, Marvel editors felt they needed to have T'Challa back off from his black Americans "MY people" position so as not to alienate the LCB-RD. However, it wasn't the "Black" that was conciously dropped from his name for reasons of avoiding confusion. It was the "Panther" that was dropped. And now I am happy to say that T'Challa is now and forever, the Black Panther---that is of course, he will be when he regains his mantle from his lovely sister, Shuri.
Two, not only would they have to get stores to sell the book, but they would also have to get the Comic Code Authority to approve the book. Given their stance at the time, it's not very likely.
Kip, Kip, Kip, Kip,
Kip!!!! 
Brother, both Avengers #73 & #74
were approved by the Comic Code Authority. In Avengers #73, T'Challa was the very embodiment of the Black Panther Party, demanding to take down the white racist Serpents on his own and referring to himself as Monica Lynne's "Soul Brother". I wonder what the LCB-RD would have had to say if instead of being written by Roy Thomas way back then, the Sons Of The Serpent story had been written by Hudlin in the here and now. Hell's Bells!
And third, the name is a very logical name for a Black hero, if you are going for a cat-theme.
"...very logical name for a 'Black hero', if you are going for a cat-theme."

I say...

Kip, are you saying that a Black hero can't be named Sabretooth, or Puma, or Wildcat,....or Bronze Tiger? Are you saying that the "very logical name for a Black hero" is to be named something with "Black" preceeding it? Like Black Lightning and Black Vulcan, two black characters often cited by the LCB-RD whenever they want to bitch about black heroes always having to have the word "black" preceeding their names?
But ultimately, I think Stan would have admitted that he got the name from the organization. No, not during the 60s, but
during the 70s, he would have.
Well, as far as I am concerned, Stan Lee did just that. He "borrowed" the name from the Black Panther party knowing that potential black readers would readily identify with the name and be excited about Marvel Comics' first black superhero. Recall that intially, T'Challa had that awful clown suit and was being called the Coal Tiger. You know by now what I have had to say about tigers and the African continent by now, so I won't....oh the hell I won't. There are NO TIGERS IN AFRICA.
So I'm still waiting for Stan Lee to admit that his decision to name Marvel's first black superhero the Black Panther was influenced by the Black Panther Party.