1. The DC to aid is the same as the DC for the skill itself, by default. (With flexibility based on the specifics. E.g. if using Deception to Aid a strike, the DC might be the enemy's perception DC.)
2. Instead of Crit success/Success/Fail/Crit fail being +2/+1/0/-1, it's +4/+2/+1/-1

Watch the video to see the logic Ronald uses to arrive at this.