I don't usually comment on this type of thread anymore, but IMO relative to your squatting style you have gotten some bad advice.
You are basically doing a high bar squat. Your form for that style of squat is OK. I certainly wouldn't change the speed of your descent or try to sit back more because both things are going to lead to you leaning in more which is a big problem with your bar placement. You basically want to open up your knees and sit down.
The main thing I see is you need to focus much more on squeezing the shoulder blades together and pulling down on the bar so your lats are tight. This will help keep your chest up. Just sitting at your computer reading this, put your hands up like you are gripping the bar and then squeeze your shoulder blades together and force your lats down towards your hips and observe what happens to your chest. It should rise and if you can maintain this position it will basically lock your upper body into the most advantageous position.
If you have the shoulder and elbow flexibility to do it, a more narrow grip is typically going to help you accomplish this. If you are experiencing elbow or shoulder discomfort, move it out some. Otherwise, keep it where it is at or consider moving your grip in incrementally as the weight increases (start out wider and move it in as the weight progresses on your warm-ups up to your work weight. This will keep you from getting too beat up.
The 350 was close to a limit lift so I think overall, your form was pretty good. In a high bar, the battle is to stay as upright as possible because any forward lean is going to kill you as the weight progresses.
As soon as you come out of the hole your focus should be on driving the hips forward as hard and fast as possible. If you just try to stand up with the weight, you'll never make it through the transition on a limit lift. The focus has to be on popping the hips forward.