The old Bless attribute IS the +10 to each stat. A charge gets used up each time you wear the item AND charges get used while you're wearing the item. When the charges are gone you are left with a plain cloak with just a fancy title on it.
Yep, this is the way they work.
Yep, once charges used up it dissapears.
No, they don't disappear. You would have a cloak with Bless: 0 charges.
Each charge lasts 1 minute. If you are still wearing the item, it will automatically use up another charge and continue the blessing on you (+10 each stat). If you wear the item long enough, all the charges will get used up.
Once you take the item off, you lose the stat bonuses. It does not last the full minute if you take it off.
There were lots of different kinds of items that could have this "Bless" feature on. I've seen rings, bracelets, earrings, leather and studded leather sleeves, boots of several kinds, cloaks, sashes, and I think studded legs and some kind of hats. Enough to think that many wearables had a chance to have this property.