1 you do thaumcraft research and you will get access to bloom crafting as well as the more advanced methods of cleaning taint
2 tainted creatures have very high damage, but aren't smart, if you are committed to going melee with them then you will just need better equipment and a full suit of iron won't cut it. Really melee isn't the method I would recommend to fight tainted creatures, personally I don't bother with meele untill mid- late game when I have a full suit of enchanted armor and a weapon with several modifiers. you could resort to a range weapon, or lava/fire, or even luring them into some kind of trap. there is no (RIGHT) way to kill tainted creatures.