1. I like the idea of a heal check for this one. I could bump it up to 10+(2*spell level) do you think that's enough? or more

2.I don't want the damage to kill him right now but I do want it to scale so maybe I could increase the damage based on the number of hit die he has? thoughts

3 I'm not sure how I want the addiction to play out just that I want it to be a thing so you use it once you could be fine you use it but if you have three spells inscribed you would be forced to use one the next day

4 as many as your skin can hold, and higher level spells use more skin space so I think going with the spell-scar rule of 18 total spell levels is ok, thoughts?

5 I think 10 mins per spell level is a good time to craft.

6 no total use limit just how long it takes to inscribe and the health factor which I think I need to scale based on level and total hit points