Do some newspapers.com (or similar site) research to see what players named Steve may have broken an ankle that season. There's a free access site that carries scans of
Sporting Life. Try that.
https://digital.la84.org/digital/col...3coll17/search
As to Melter's autograph, I only have one--from his 1918 WWI draft registration. It's signed with his full name. The "Steve" on yours doesn't really match up with the Stephen on the card. His middle name started with a B, which slightly matches up with the capital B in the address. Same with the capital M. Maybe, maybe not; not enough to say one way or the other.
Keep in mind that I can't tie him to Superior, WI in my very basic searching. Doesn't look like he ever played there. He was born in IA and was still living there as of 1918. Died in IN.