Here's the Salary, it's in SEK. The different steps are; 1-2 years, 3-4 years and so on. If you're a direct entry captain then add 19.000SEK. You'll receive roughly 10.000SEK on top of this, thanks to duty hours payment.
Season flexibility is, as far as I understand, possible for SAS with just the next months roster release, degrade your hire% down with 15% during 5 months.
Regarding an upgrade to mainline, this is not possible. It's a completely different seniority list and the list for re-hires into mainline is quite long (roughly 450 pilots are waiting to be re-hired).