Can I have a husky without joining the vampire hunters in Dawnstar? Are the husky immortal?
How often dragons and vampire attacks in towns? I haven't do the quest in Whiterun where you need to talk to the yarl about the dragon. So I'm safe from the dragon attacks and my character is not yet prepared.
Can you survive skyrim without maximizing smithing, alchemy and enchantment?
You must complete the quest A New Order to recruit them. That means you have to side with the Dawnguard and get as far as listening to Isran mouthing off. What you do after that point is up to you.
They aren't quite immortal - what they are is Protected, which means they can only be killed by a direct hit from the Dragonborn. They won't die from NPCs, fall damage, or stuff like that.