You have nothing to remove Necrofear from the Graveyard, if you'll keep on destroying monsters, he'll summon it and then what? You'll destroy it with Scorpion? But his effect and DB ability will activate. You lose.
You could use pot of benevolence to prevent him from summoning necro in the first place. as soon as there are two monsters in his garveyard you should get them out there again. the he can't activate his skill or steal one of your monsters with necrofear that way.
Yes, he has. He can activate the destiny board skill if he's at 2000 LP or lower and you send his necrofear to the graveyard, or he steals one of your monsters with it. I'm not sure when he'll activate the skill and when he'll steal the monster though.
It says make sure to 🔥 doll of demise (even if you have to sacrifice the only effect damage) when he summons it because he will activate ectoplasmer after (its the way the ai works)