Re: How far can a male pull back his foreskin?
As long as it will go back behind the head, when you are erect, easily and with no pain then everything is fine. If you dont like it bunching up then you could try stretching the frenulum but that is likely to increase the risk of spontaneous retraction when you are swimming. The bunched up area forms the ridged bands which are full of nerve endings and very sensitive, to touch and to the movement of the foreskin back and forth. If you gradually expose your glans to stronger and stronger touch then it will no longer be painful if the foreskin slides back inside your trunks. Start off with the spray of water in the shower and build up from there.
You pull your foreskin back to put a condom on (put a drop of water-based lube inside the part that encloses you glans) but otherwise it's easier to enter the vagina with the foreskin forward. The gliding action as the foreskin slides on itself acts like an extra lubricant to make entry easier. During intercourse the foreskin should slide back and foward over the glans.
Hope that answers your questions,