A few minor additions
(a) Magical items have the Enchants stat. This stat tells you how many blessings/enchantments have already been cast on the item for you. Your Blessings (or Enchants) skill must be higher than this value and you can add only (your skill - Enchants stat) blessings or enchantments. The blessings and enchantments stack together so that, for example, you will need either Blessing 7 or Enchants 7 for 3 blessings and 4 enchants on the same item. Yes, some items cannot be blessed (or enchanted) at all even if they have lower Enchants stat than 12 (or have no Enchants stat at all).
(b) Yes, +42
Let us also mention Ardibren's Keepsake. Well it's a quest item but it can be inherited from game to game (so that you can have more than one Ardibren's Keepsake in the end) and it can be enchanted. You can add 12 (or 14) blessings to it. Armor blessings can be added and they are also "+1" like in the case of rings or bracelets. Therefore, +56 plus some Frost Resistance if you want
Use "Judge Ooka" method in the Guild if you want your private Ardibren's Keepsake.