If you are practicing masturbation you have to be very careful that in the heat of excitement you don't seriously injure yourself. Could that vein be injured because of subjecting your penis to unnatural stress--such as a vacuum pump?
http://www.actionlove.com/extra/penilepump.htm
I have read about some men who have developed priapism after using rubber band like attachments at the base of the penis in order to stifle blood flow and make the erection harder. Once the compartments which hold the penis blood are damaged, the penis stays damaged. So I seriously suggest you avoid anything that causes you even the slightest discomfort.
Better safe than sorry for a lifetime later.
The white pimple-like things you mention might be caused by poor hygiene.
Especially if the male isn't circumcised. In any case, see your urologist as soon as possible.
BTW
The natural upward angle of entry is in accord with the male erection. But if the angle of entry is forced into a horizontal one then damage to the penis can occur.