Elrond was indeed much mixed blood (with the human elemts somehow purged by the Valar when the choice was put to him.
Thingol (Sindar)was his great great grand father, Turgon (Noldor) was his great grandfather. Staring from those generations as best I can figure Elrond (before being made all elven) was 6/16 (not quite half) human, 4/16 Noldor, 5/16 Sindar (based largely on the ASSUMPTION that Dior's wife was Sindar), & 1/16 Maiar (from Melian, Thingols wife). Going back further is is even more mixed, with some Vanyar & Falmari blood IIRC.
He was consider Lord (but not High King) of the few Noldor remaining in Middle Earth, he and his sons (Elros having chosen to be made all human) representing the only male descent of Finwe and the Noldor kings remaining in Middle Earth.