In a pre-modern society how many people need to be farmers to support a non-farmer? Like whats the percentage? More than the 99 to 1 for soldiers, would 9 farmers for 1 non-farmer make sense?

9 to 1 is way off. 

A knight’s fee was a common metric used for fiefdoms – larger estates were usually calculated in multiples of knight’s fees, smaller estates in fractions that led to the imposition of scutage – which is meant to represent the size of land needed to support one knight. 

A knight’s fee works out to five or more (I’ve seen 12 cited most often) hides, and a hide of land was supposed to support ten families. So a knight’s fee would have around 50-120 families living on it, and given an average household size of around five people during the Middle Ages, that works out to 250-600 people to support a knight.