Yes, accutane should help with pustules.
As far as I know, a lot of people find their skin appears a bit redder in general while on accutane, and therefore scars/pigmentation you already have look a bit redder too, but they would fade again as usual after you stop taking it. I'm not sure if this is the skin actually thinning or something else happening. As the skin is more delicate and dry while on accutane, if a new scar is created while you're taking it, then yes I think in that case there is more of a risk of it being a 'worse' scar, but if you moisturise it well, it also might not scar at all.
Basically things might look a bit more pigmented during, but should be fine/normal after.
I'm new to accutane and that's what my research has led me to believe, but maybe someone who has been through a round or two already can add their thoughts