I am from Seville, even though I do not live there since 2001 I go there once or twice a year.

1- 60 mins before you are fine, unless you want to wait in the lounge (which is not great but you have toast, sandwiches, booze,...)
2- Priority check-in shall be fast, even though normally there is only 1 counter. Security is never busy like big airports. Maybe on a Mon morning will take you 15 mins. Air Nostrum is fairly quick on boarding, you will get a shuttle, leave the your handbag suitcase before you get into the plane. The overhead compartments are pretty small. They will give your suitcase back once you pop out from the plane in MAD.
3- Traffic 8am is normally hard. 45mins to be safe, may take you less but honestly I do not think 19 mins is realistic at 8.00am