theres no way a 1/4 inch adapter can take the stick a sump plug will give. Use 1/4 inch for small or light jobs only. i.e. bolts requiring just a small amount of torque
Just a thought - as you're using a bar, not a ratchet, you are turning it the right way aren't you???
Sump plugs should only be done up to approx 20-25lb ft, so obviously some complete moron has worked on the car previously.Anti-clockwise is the correct to remove