Personally I think your form is quite good now except asymmetric bar placement on your shoulders. I would still recommend also you to try wider stance if you see knee moving as a problem. In your case wider stance would allow more room for hip and stomach which now might push your knees forward at the bottom position.
One guy at our gym (national champ. 685lbs squatter) has similar knee slide. He is belly guy who squats bit over shoulder width stance.