nope
If you are a vampire, a blood potion replaces the need for a feeding.
Kill a monster and get it from it
You have to kill a will-o-wisp.
look for a oblivion gate and kill deadra that is how you get the hearts you can clone them
In fact there is no Exp on oblivion but the higher the difficulty the longer it takes to kill the Creature/Person which means the fight lasts long enough to increase one of your skills.
The only way is to kill bears.
To obtain the Flamesword You must go to the Chorrol North gate and kill at least one person no guards with the blade of Woe then you will have the Flamesword.
I am lvl 15 and I can buy them.
sneak attack with a strong melee
No. The only way to get rid of it is to kill it.
Kill with fire
Because you've been infected with vampirism, and did not cure it in time.