For the back acne, plain white vinegar should help with that. It was recommended on the show, The Doctors.
Normal! All normal! You will find out that there are also ladies out there who like a hairy chest and arse as you call it. Difference in being a boy or a man! If it offends you, you can always have it removed.
The hair is not a problem; some men have a lot, while others have a little. Every body different. You could see your doctor or a dermatologist about the acne.
Everything you describe is normal. It will not scare girls off. Some kids in your school at your age and even younger might have a lot more hair then what you have on your body.