Why did it count me wrong for using double 's' in place of the odd B character? I was told they are the same thing
They are not the same thing, the correct is with the eszet ß. Its replacement with ss or sz is merely an acceptable exception given when you can't use special characters, like in an ASCII operation. Doulingo wants you to learn the correct usage.
Pronunciation is the major thing ruling over them. The eszet ß, as defined in the latest German standard has a faster sound than ss or sz.
And for clarity, it's not an odd B, it's the evolution of medieval writing of sz. Its use has a lot of literature and culture background.
While ß is more correct ss should be an acceptable substitute considering not all users have the skill to add alternative keyboards. I'd report it as an error.
For the PC, duolingo already added buttons for special characters. As for mobile phones and tablets, simply click and hold the s button and an extra letters will appear (including ß) ;)
Because in English, pronouns have special possessive forms -- we say "my book, your book, his book, her book, its book, our book, your book, their book" and not "I's book, you's book, he's book, she's book, it's book, we's book, you's book, they's book".
(Mis-spelling "its" as "it's" is a common error from native speakers since the pronunciation is the same. Similarly with "your" are "you're". But those possessives have no apostrophe in English.)
Is there a difference in translating it out as "he is called" and "his name is" or are bith correct
Not really, but "He is called" sounds odd in most situations. "His name is" is (almost?) always much better.
The meaning is the same, but when Duo gives you "He is Hans" most people would translate it with "Er ist Hans". That's why "He is called Hans" is the preferred translation for "Er heißt Hans".