OK. Relax. A curve to the penis is completely natural. Most men actually have one. You have hypersensitivity to sexual stimulation. Do you ejaculate fast? If so, there really is nothing that can help...all you need to learn is self control. Trying different positions and other methods of stimulation might help, but are not gaurenteed. If you don't mind me asking, what is your erect penis legnth?
1) Not straight is fine.
2) Forget about your length. There is nothing you can do about it. Your length will be fine, all men want to be bigger and usually they are perfectly long enough anyway. Worrying about it will only make it worse. You need to accept and be happy with it. When men do that, that is the best thing for them and their woman. Trust me.
3) As for the sperm, you have to teach yourself. First off, don't touch the tip of your penis when you masturbate. Focus on the shaft. Also, be gentle. A woman's vagina doesn't grip your penis tight like a hand.. It is soft and gentle. So you have to make your hand soft and gentle.
Then, you have to masturbate and just before your sperm comes quickly (ejaculate), you have to stop completely and take your hands off! And hold it and wait. Then in a moment, when you are a ready, start again, and do the same. If you keep stopping before you ejaculate, your body will learn and you will last longer. Eventually you can go for a long time, and you will be in control, so that you only ejaculate when you WANT to.