Crafting and Cohort questions

[Sergeek The Mad]

So I'm trying to build crafting stronghold via "Leadership" feat, so here is two questions:
1) What is the maximum level Cohort can achieve? 17 or 18?
2) Is there more rules other than those about custom items creation? What if I want to build an item with luck skill bonus? Or with a bonus to critical confirmation?

[kestral287]

1. 17th
2. The rules are "talk to your GM"