This sounds not like acne but from folliculitis caused by shaving, resulting in "razor bumps." I'm not sure how to interpret "that remain red and scarred, basically burned." Red marks can take months to fade, but persistent redness doesn't equate to a burn. On the other hand, you may be aggravating things with benzoyl peroxide, which wouldn't help anyway. I advise you to leave the area alone, and trim the hair at most, rather than get any kind of close shave. If that doesn't solve things, you'll need to see a doctor in person.
Take care.
Dr. Rockoff