Yeah, go down to about 170, or whatever weight where you can keep your knees out and your back/abs tight, then resume linear progression from there. It may hurt your ego, but cleaning up these form issues will help you to break through your 226 barrier.
I still think it would be helpful to see a side-on 90 degree view of your squat to get a clearer idea of what's happening with your bar path.
Re: point 2 - you may have just set up with your hands and shoulders a little off center relative to the bar.
Re: point 4 - arm pain from low-bar squatting is quite common. In your case, the bar may be slipping down the back of your shirt, putting pressure on your arms. Do you have chalk? Rub some on the back of your shirt, where the bar sits. This will help. Also, chin ups help heal arm pain from squatting. Consider doing 3 sets of chin ups after every workout as therapy for your arms.