About second question: You can't alter wolf form appearance, I believe this is intended.
About third question: They'll turn back into normal sims with next morning (between 5 and 7 AM depending on season/ 6AM without seasons EP).While they'll try to bite your sims, they can't enter your house, so as long as your sims stay inside they are safe. They will also not interrupt or change order in your queued actions, so as long as you keep an eye out, it's safe to have sims outside too. They might be quite an hindrance as the game will often make elder sims appear, and then die on your lot, so unless you move their tombstone to graveyard, they might haunt your property.