Your bio should be the save viscosity as dino. Check with Fabman, mine is but im in AZ with warmer temps.

What was the outside temp?
WVO is guaranteed to take out a pump (it did on mine) so if the transvercification process failed its just super clean veggie. Cut up your percentage a little, I know that the dealers up north dont sell in winter because of the gellling issues they have. Personally I bet your doing everything right and its just a bad pump. Mine went after 400k miles and 1 tank of WVO. New one is just fine bio or dino. 522k miles plus on the truck now.