I think a lot of your questions can't be answered in general, but are down to your personal level. Your capability to endure pain depends on yourself, every subs/masochists is different. Even a sadist can't "look into you" and know what you need and how much of that. Communication is key here, to get the pleasure you want, not to little of it, but also not too much. And don't forget, there is a difference between a bdsm relationsship, and an abusive one.