How do I measure the difficulty of enemies/bosses/monsters by point totals (compared to PCs totals)?
You don’t. Balance and combat difficulty depend on combat skills, damage output, defenses etc. Point totals have little to do with that, unless you compare two ‘pure’ warriors (all points go to attributes and combat skills/advantages). For instance, you can have a 300-point king (Wealth, Rank etc.) and a 75-point assassin. Naturally, face-to-face, the assassin has a pretty good shot at taking the king down.