Headlock Variation
BG jumps and grabs you in a headlock in your guard. His back leg is up and out again. Use the elevator sweep. Just make sure to trap his headlock hand.
Jiu Jitsu Drill: Practice the elevator sweep and get the straight armlock from the mount (both BG pushing and BG turns to side variations)
Remember: If the BG tries to crush you with their bodyweight, check to see if their leg is posted out. If so, use the elevator sweep. If it doesn't work, just go back to stage 1 punch block and remain calm until something else presents itself.