Matt Darcy teaches a triangle escape for when your opponent starts locking the triangle up and your elbow crosses their center line.
In this stack pass escape Matt Darcy times it for right when their hands connect. When they do he extends his body, pushes the hands upward, and frees his knees from their hold.
Using the foot scrape to escape from mount to half guard, Matt Darcy urges his student to keep that momentum going to get to their strongest position to get the finish.
When going for the north south reversal, the main reaction will be for the opponent to rip out the arm that is being trapped to prevent their post. When this happens it creates enough space to be able to regain a guard.