I know that students from Yale, Harvard, Stanford etc will often say SLS/YLS/HLS and it's totally acceptable. What I did was I would spell it out the first time, then use the abbreviations for any following reference.
... like Yale (61%), Harvard (57%), Stanford (50%), and Chicago (61%) -- or ... like Yale (61%), Harvard (57%), Stanford (50%), and Chicago (61%) -- or ...
Did you write the optional essays? December isn't early, but it's not super late. Getting WT from Michigan and Duke with those numbers makes me think the schools didn't think you were serious about attending.
I took the January 2015 LSAT (might have been Feb?) and used it to be accepted to T14s that cycle. The only school that wouldn’t accept the score was Stanford. Good luck and I hope that helps!