I don't see the case of normal or carried items, and there are some questions:
- If item is carried by anyone, what lvl do you use?, the character or the item one?.
- Is normal items lvl 1?.
- In any case, should we add some value to RRs for item 'resistance'?. For example, the spell 'destroy solid' including metal, you could add the material bonus to RR (+5 or +10 to steel, +15 or +20 to alloy, etc.). See that this modifier is usually used when the item is damaged, if not there is no reason to add the material resistance.
The last two I suppose that are correct (or is used mostly), but the first one is not clear.