if your yeast has been sitting for a year then the mrmalty calculator is going to give you a very low viability. like 5% or something. that's why it gives you a number like 4 liters for only a 1.048 beer.
the real answer is that mrmalty isn't sufficient for your situation. you need to step up your starter from something small at first, to verify viability.
YeastCalc Yeast Calculator
that tool gives the same results as mrmalty, but is designed for multi step starters.