Some custom spell and magic item questions.

I have a couple of questions. I apologise if these are just somewhere we missed, but these are things that my Judge and I couldn’t find the answer to.

Firstly, the Player’s Companion lays out for protection spells a differance between immunity and resistance to a type of damage, but I cannot find and examples or rules for how resistance works.

Secondly, when creating a magic item that casts a spell, how many dice would it use, especially if it is a custom spell? When you make a new spell they all deal a number of dice based on level so I am just wondering if there is any rules or flexibility in putting this in rods, staves or wands.

Thanks!

Resistance to a damage type gives you +2 to AC or saving throws (as appropriate) and -1 damage per die (minimum 1 damage).

Source:
http://autarch.co/comment/24670#comment-24670

As to the caster level of charged items, I don’t have a RAW answer for that either. Scrolls (and presumably items with identical mechanics in a different form) are cast as per the minimum level required to cast the spell (ACKS Core page 216). Based off the damage dealt, wands appear to be a 6th level caster and staffs an 8th level caster; however, in the item creation system, there is no distinction between staffs and wands; they are both just multi-charged items.