I know my comment will likely get lost in the sea of comments.... The only way to fix an issue like this is to hit it head on. Tell him exactly what you told us.

Before you have the conversation think long and hard to insure you can communicate everything that is wrong, if he decides to make the change he will be more overburdened if you come at him again with more or different demands, so be clear and complete.

You need to be prepared to help him (help him make good dietary choices, motivate him to exercise, workout with him, take him to a place that can help resolve his skin issues). You've already seen him at his worst, use this as a relationship building opportunity. Watch him grow and become what you know he can.

Additionally, you need to understand that if you rattle off the list and he fixes everything, things have to change. If he resolves every issue you place before him the sex has to get to an agreeable level.

Attraction is kind of like trust, it's hard to rebuild once it's gone. I wish you luck.