Thanks for your query. Based on the facts that you have posted it appears that you are watching porn Videos regularly and comparing yourself with what you see in those videos.
First of all i would like to state that those are not realistic and are photographic tricks.
I would to answer your questions point to point.
1) Any Girl or woman is interested in getting sexual satisfaction and not on size or length of a penis.
does not affect sexual potency in future.
3)Quantity of semen depends upon how frequently you are masturbating and it does not make any sense as far as fertility
4) As per your statement you r penis length is 5 inches wish is normal.
You can consult qualified for Urologist
for help.for any problem.