Bathing is an unnecessary ordeal for you and the cat. A bath rarely does anything positive and if anything might give the cat some skin problems.
As for scratches, even if you out of desperation began to think declawing was a feasible solution -- you are forgetting his teeth. He'd just start biting harder and absolutely nothing would be solved.
To get to the core reasons, like several people have already said, (1) this cat probably needs some additional time to acclimate to you and (2) you need to learn how to read a cat's body language. Nearly all of these "attacks" were the result of you doing something bold without the benefit of having built a trusting relationship, or you inadvertently missed his signals telling you to "BACK OFF!" when he wanted to be left alone.
Here's an example of watching a cat's tail:http://18.104.22.168/~emailbox/tailtalk.htm
(Nano is pretty much half-wild and more semi-feral than housecat, but by learning her body language/sounds and patiently letting a trust build over the course of time, I rarely get injuried even when I have to thoroughly handle her or get her to do some things she'd prefer not to do.)
So...here's a concrete example:
Let's say you can pet him for 30 seconds. He is purring for a while but then he suddenly bites you or scratches you. Well, it wasn't "sudden" -- whether you saw it or not, he started asking to be left alone around 15-25 seconds and you just kept right on going. Did the tip of his tail start twitching? Did the tone of his meows change? Great, so what is the solution? Pet your cat for half the usual time so you get the favorable interaction without going too far.
(If you are trying to make him into a big time lapcat, you can gradually increase the amount of time he is petted until he becomes more accepting and learns to crave the attention. There was a cat available at Petsmart that had belonged to an older woman who had died after a long illness. The foster family taking care of this cat said it would spend 14 hours a day in someone's lap -- nonstop wanting to be petted. So obviously the cat's previous owner had spent most of her waking hours providing a warm lap. So if that's what you want, prolonged affection can be built up over time...but it won't happen right away.)
Good luck with things!