If ldl cholesterol is known as the "bad" artery clogging cholesterol is there a healthy level?

Less than 100 : Ldl that is less than 100 is considered optimal. If you have heart disease then your doctor may recommend that it be less than 70.

LDL Not Cholesterol: Ldl & HDL are lipoproteins, i.e. Protein particles which carry all fats in the water outside cells. Ldl is always in nmol/l, best <700, HDL in µmol/l, best large-hdl >10. See NMR particle test, <$100. Yes, LDL particles are primary driver of ds. Cholesterol is a fat made by every body cell, cholesterol not best test, ldl-c calculated, not measured & often misleading, but promoted because cheaper.