Thinking of allowing Strahd as a warlock patron

How do you deal with a fighter who sneaks up to a guard and attacks the guard?

Do PCs need to take a long rest before leveling up?

Do you count summoned creatures to calculate the CR difficult?

Should I do a new card reading at the start of every Curse of Strahd session?

Is Wild shaped Druid considered a beast for the purposes of a dryad’s charm ability?

Is the extra 1d8 damage from the Ranger’s Colossus Slayer mandatory?