12 Biggest Unanswered Marvel Movie Mysteries

In Iron Man 2, Tony Stark discovers that he can synthesize an incredibly rare element (which was called Vibranium in the novelisation, but that was retconned and the Avengers prelude comic says he tried to patent it as Badassium). The element helps stabilise his Arc Reactor and stops it killing him, but clearly the intent was for the element to have the same sort of uses as Vibranium (or it would never have been called it).

So, why doesn't Tony use this element that he can generate himself in the outer armour of his Iron Man suits? Wouldn't the augmentation of them with a near indestructible metal be sort of useful? Particularly as Stark had to actually fight a robot villain with a Vibranium outer casing in Age Of Ultron. You'd think that might have jogged his memory about his own super element existing...

Also, will we ever learn the secret of how Howard Stark came to be in possession of enough raw Vibranium to make Captain America's shield? It might be explained in Black Panther's solo film, but that would presumably mean that Cap would need to cameo, and as far as anyone can tell, Chris Evans isn't contracted to.

It just feels like something of a continuity gap that should have been explored already, given that there have now been six Cap and Iron Man films in total (minus the Avengers team ups).