Okay, woman's opinion:
First thing: don't worry about the dimples. No offense to any guys out there, but even so-called "perfect" penises are not very attractive. They just aren't. There may be women and men who would disagree with me (feel free to), but I would say that most women would say the same thing. In other words, you don't have to worry about how good-looking yours is because none of them are that great. If you think the dimples are some kind of medical issue (you said they were spreading?), then you should have a doctor take a look.
Second of all, yes you may still grow, but even if you don't, it probably won't matter that much, especially if you work on using what you have effectively. Any girl in her right mind would take a guy with a 3 inch penis who knows how to use it over a guy with 7 inches who doesn't. Also, there are women who are small, too. A larger penis can be painful for them, rather than pleasurable.
The difficulty with ejaculation during masturbation may be due to your lack of confidence or just lack of physical maturity. Stop focusing on the quality of your ejaculation right now. If it's a problem in the future with having kids, then worry about it, but not now.
As for being afraid to have sex, don't worry about that right now. You don't have to have sex just because you are dating someone, especially when you are only 16. Find a nice girl and build a real emotional connection with her. If you guys find that you want to have sex, if she loves you, she won't care how big your penis is or how it looks. She'll only care about you. Most women can't have an orgasm through vaginal intercourse anyway. They need manual or oral stimulation. Get good enough at that and you'll be just fine.
Trust me. What you are going through is normal and none of it should interfere with your life.