Hi. Do not use benzoyl peroxide on your penis as this will cause stinging and irritation.
For the acne on your face, ask your doctor for a more effective treatment such as Duac gel (clindamycin and benzoyl peroxide) or Differin (0.1% adapalene).
Also mention the spots on your penis. These are unlikely to be acne vulgaris, which commonly occurs on the face, chest and back. It is easy to get a bacterial or fungal infection in the genital area and this is not the same as an STD.
Best Wishes, Eloise.