You can't keep your back arched with your work sets, but this guy wants you to do high-bar squats with advanced Westside programming? I think you should back off, learn how to get voluntary control of your lumbar muscles, and work back up to 245 with better form. Don't confuse a lack of progress with a lack of programming complexity. And your back angle for a squat should be more vertical than for a deadlift unless you're pulling sumo.