The area you are talking about is usually enclosed tightly in underwear for most of the day, so it's not unusual for it to become sweaty. That probably explains the "sour" smell. Try free-balling as much as possible. I would not recommend putting powders, creams or oils on your genitals because it's just not natural. Even soap can produce reactions that make you itch down there.
You do not have a yeast infection -- you're not constantly scratching, there's no rash, no excessive redness. If anything, you are worrying too much: this is obvious from the fact that you have to "bend down like four inches" from your scrotum to detect a smell. Guys don't normally do that. If a chick is going to go there during oral sex, it's obvious from the description of your hygiene habits that she will have no
problem with your smell, particularly because you retract your foreskin and wash that whole area when you shower. In any case, normal body aromas can be sexually attractive!
I also have tiny bumps under the tip of my scrotum they are the size of grains of salt but get bigger if I am more erect.
These bumps are normal; all guys have them. They are hair follicles and you're right: they do
become bigger when your penis is erect.
If you want your partner to "smell nothing but roses" when you have sex, use some deodorant. And make sure you use condoms.