1) First of all, as I've already mentioned, comic books tend not to be overly restrictive or to have too much ownership about character races/appearances anyway. Characters are often reimagined either intentionally (e.g. the Nick Fury -> Samuel L. Jackson transformation) or subconsciously (the characters are drawn by many artists over the course of their publication histories, all of whom have different styles or ideas about how these characters look or ought to look). If Iron Man always looked exactly the same in every single issue of every single series since the beginning of time, and the community surrounding comics were proud of this rigid, static, constant idea of character identity, that would be a different thing, and then I would be more concerned with these film adaptations that were trying to change characters fundamentally. However, this is not that community, and for decades, there have always been these reimaginings and reformulations of the same stories.
You are conflating multiple things. The differences in the look of Iron Man are due to the differences in the way that different artists draw, and different suits of armor created by the character. Tony Stark has always been a white man with dark hair and a mustache. The character has always been the character. His hairstyle may have been drawn various ways over the year allowing for different trends/what looks cool/different artists, but you can always look at Iron Man or Tony Stark and say "That's Iron Man" or "That's Tony Stark."
Movie adaptations play into this. Marvel movies are a somewhat newer thing, but if you cross over into Batman-land, you'll see that there are a lot of takes on Batman. You've got the campy Batman from the old TV show, the series of movies in the 80's and 90's that all sat in different places on the dark<---->campy continuum, and the recent Nolan trilogy that was pretty firmly rooted in a dark, gritty realism and plays on a lot of modern issues (terrorism, violence in American cities, and so on and so forth). Wildly different movies, wildly different aesthetics, wildly different scripts/themes, and you've got a few different actors with wildly different appearances to boot, and yet all of these Batmen are still Batman. They're all just differing takes on Batman, and we've always had the idea that comics are a place where it's okay to have different takes on what is still fundamentally the same character. This gives me no reason to believe that anyone in the world should be offended by casting a black actor in the role of a superhero who's been traditionally white (as long as, again, the casting doesn't make the movie nonsensical).
And no matter what new take was taken on the mythos, Bruce Wayne was always a rich white man whose parents were murdered in front of him as a boy, and whose motivations (and neuroses) grew from that.
Comic book movies tend to draw from a particular storyline in a particular series, may recreate famous scenes from particular issues, and will tend to draw from the comics for guidance regarding major plot points, but to my knowledge -- and correct me if I'm wrong -- no comic book movie has been a shot-for-shot remake of any series of comics, nor do comic book movies in general try to mimic the tone or visual style of any particular series.
Depends. Frank Miller's take on Batman definitely had an impact on the tone of Burton's Batman films, and his story Batman:Year One reads like the script for Nolan's Batman Begins. And the Sin City films really are almost panel-for-panel reproductions from the comic page.
But there are always changes made when adapting stories from one medium to another. Doesn't matter if it is going from a novel to the screen, or the comic page to the screen. Different things work in some mediums that don't in others. Whether it is conflation of multiple storylines together, to condensation of a particular storyline for purposes of running time, or wholesale narrative changes (see Peter Jackson's LOTR trilogy), or even changes to the way things look - sometimes something looks great in the context of a two-dimensional handdrawn comic page, but can look bulky, cheesy, or just ridiculous if "faithfully" reproduced in real life.
The race of your characters seems like a weird thing to latch onto in this regard; if we're going to complain about the visual incongruity between the movies and the comics made by casting someone black, it seems like there's a hell of a lot of stuff you should be complaining about before that, like the fact that everything looks totally different and all the dialogue is made up. To skip over all of that and focus on race seems disingenuous, especially when -- as we all agree -- it doesn't really matter whether most Marvel characters are black or white.
Well, I just gave of list of common changes. But race is not ever one of those things that need to be changed in adaptation. There may be good reasons to change a character's costume, but there is no narrative reason to change the race. That's all I'm saying. There might be legitimate reasons to make all kinds of changes in adaptation, but the race of a character is not really one of those things.
I come to the films as a fan first of these characters I loved from comics. I understand that some changes need to be made, but given that, I hope for as faithful a translation as possible, because the love of the characters and stories comes from the comics. So willy-nilly changes for no reason bother me, as they rarely do good things for the film concerned. Which is one reason, I think, that the Marvel films have succeeded. They don't shy away from things in the comics, they are faithful translations in the essences of the characters.