Well, the organized crime/casino connection isn't totally unfounded, but there's no doubt that he was being incredibly insensitive toward Native Americans. That being said, he is far from the exception there. EVERYONE is racist toward Native Americans (not condoning as it is horrid and one of the most underrepresented minorities in the US). Bernie isn't mentioning the natives, Hillary isn't mentioning the natives, tumblr isn't mentioning the natives. They are often overlooked and mocked by many Americans, so that is less a Trump problem and more a national problem. Especially back in the 90's.
I'd address the 1973 comment but 1. no source and 2. when I looked for one I was inundated with buzzfeed and huffpost articles with their bullshit lists, so I couldn't find anything credible.