Hey Fayewolf, glad to see you back again...
For your heelside issue, the reason most people struggle with this is not committing to the turn and not turning their head over their front shoulder to look down at where they want to go. I see people in my classes day after day trying to make this turn but remain looking up the hill. Additionally, the best way to to manage speed is to flex down low to initiate your turn and extend up through it as we discussed last season. The reason you go flying off to the side so fast is you are remaining too static in the turn and not getting nearly aggressive enough with your movements.
Skidding your turns is not necessarily a bad thing if you are skidding at the right stage of the turn. Your snow spray should being thrown to the side of the run not down the hill. If all of your spray is going down the hill, you are delaying your braking action and doing it at the bottom of your turn. Instead, get more aggressive with your edge earlier in the turn and start your skidd near the top of the turn, through the control phase then ease up at completion to reduce this slip down the hill.
For your toeside steep terrain freak out issue, again, get lowere, much lower. This really helps with the fear as well as board performance. In addition, if you are freaked out going into the turn, chances are you are holding your rear hand out in front of you to "catch yourself" when you fall forward. I see this all of the time. When you go to initiate your toeside turn on steep terrain, get that back hand behind you and drop that front shoulder like your are diving into the turn. It will feel "wrong" and scary I know, but it is the only way to stay in control on steep terrain. Leaning back uphill is causing the the dealy in turn initiation and completion and causes the speed buildup.