Hi! Sorry for taking so long to get around to answering..
About combat.
For Ferocity, the creature rolls, if it hits, you can choose to allow to give the player a SURVIVAL roll to dodge the attack, unless the attack is something they couldn't dodge, for example if the creature had them pinned.
For horror, the players have to roll under the monster's horror stat. The monster doesn't make that roll.
About Magic.
1. Yes!
2. The player has to roll under 15% to start off with. Magic is very powerful but hard to do. You can widen that 15% if you want by having the player using ritual items, or herbs, or talismans to boost their magic. But essentially if they nail that 15% they can go "and then this happens" and you can't contest them (within reason) because magic. Either that or you give them some "Monkey's Paw" type version of their spell happening.
3. Your magic points are = the stat you assigned to your magic powers