I'm not sure how to increase my edge angle without toppling over and/or pulling my flank muscles... I suspect I need to actively "push" forward my inside/uphill foot when entering a new turn? As of now, I just let my feet passively position themselves. I also wonder if I need a much wider stance; as of now, they're at comfortable shoulders' width apart, maybe with a space for x1.5 skis to fit.
You don't want to simply pull the inside (uphill) ski back, you also want to tip your inside foot to the inside of the turn as you pull it back. Hip width apart is good, you want vertical separation, not horizontal separation. You don't want to push on anything. You will be receiving pressure as you carve the turn and you simply want to manage that pressure. Even with pulling the inside foot back, tip lead of the inside ski can happen naturally as a result of bio mechanical physics, it's not necessarily a problem unless you always have excessive inside tip lead.
Now, there's a lot more going on in that paragraph ^ that is not said. So if any of that is at all not resonating with you, then take a lesson. Well, you should probably take a lesson or two, three, four...many, anyway - we all have and still do. Even expert/professional skiers seek lessons, or coaching from time to time.