Regarding High Arcanas, I know for a fact that getting them from Espers isn't the only way. I think rare monsters can drop them occasionally if you have the Canopic Jar in your inventory. Also, I believe you can trade things in the Bazaar to get the High Arcana, too, using regular Arcanas (dropped by all monsters if you have the Canopic Jar) and another ingredient. (I want to say Gysahl Greens, which you can buy). In any case, High Arcanas are unlimited.