Varicocele is a diagnosis of a blood vessel, that runs from your testicles to your heart ( to put it simple), and that blood vessel is too large, and drains the blood back to your heart to easy. This can cause you a lower fertility rate. I did google the term.
I do not think that a small penis is caused by this - never heard of it before, nor is this the reason for premature ejaculations. What do you mean by premature ? It is normal that a intercourse lasts 3-5 minutes, and that porn is a big fake - all footage cut and pasted together so it looks as if the guy take ages to ejaculate.
You can however, start to practice a « stop and go» technique when masturbating, that is that you masturbate until the point of ejaculation, and then stop until the sensation is gone, and then continue masturbating again. ( it is also called « edging») Do this 3-5 times before you let yourself ejaculate - and you will explode in a very strong orgasm. The more times you stop, the stronger the orgasm will be in the end. At the same time you will learn to control your sensation. Another thing you can do when getting close to an orgasm, is to take one hand and push upwards right behind your scrotum. This will also make the sensation go down a bit, and you can continue. You can of course use these techniques during sex/intercourse.
Penis didn’t grow completely ? I do not think that is the case, as varicocele effects the testies, not the blood vessels inside your penis.
Good luck