putting your feet out wider will be easier. the range of motion is smaller. i squat with my heels just about under my hips and my toes pointed slightly outwards.

really using all of your hip and glute muscles is hard for alot of people. there are a ton of muscle that you have to engage and it takes some practice. i still really have to focus on it when i warm up.

also, you don't necessarily want to arch your back too hard while you have a ton of weight on your back. hyperextension is good for some lifts but you want to keep a straight torso with your chest up for heavy squats.