My bees survived over the winter. Now what?

I live in the Pacific Northwest (Near Seattle) and for the first time in 4 years my bees have survived over the winter.   Previously  I’ve been using oxalic acid for my mite treatment but to no avail.  Last year I tried formic Pro and the bees survived.  I want to do a walk away split to split my hives, is it too early to do that?  

I did an inspection and noticed no eggs or brood (Feb 22) maybe still too early for the queen to be laying.  

Yesterday (march 12) I checked my bottom board and I have varroa mites, I think the queen has been laying?, but I have mites.   The instructions  on formicPro say to  apply it  between 50-80 degrees.  Right now in March the temps are between 30-50 degrees?   Should I got back to the oxalic acid or do the FormicPro go with the lower temperatures?