Do you accept and/or expect structure, rules and limits as a part of your submission?
How do you feel about them?

Yes, he has rules, with "obey" being the most important.
Some other examples:  no country music if he's in the car (driving or riding).   Don't give out our phone number without permission.  Get the mail in every day.   There are a bunch of other ones, too, that have passed very much into my habits so I barely think of them as rules anymore.
I feel they are important in that they let me know what he expects from me.    If he took away all the rules and structure I would feel more than a little loss.

Does any element of BDSM occur as a part of your submissive relationships?
How do you feel about BDSM?
Is it core to your submission, peripheral or non-existent (other than the submission part)?

Yes, BDSM is a very important and enjoyable part of our relationship.   I like it very much, and even at the times when I'm not actually liking it, I still crave it.  
Bondage- yes, absolutely wonderful!  Discipline- very much required from me.   Domination- this is the stuff.   S/M-  I really get off on a bit of this.  I'm not into huge amounts of pain, and he's not really a sadist (well, maybe a bit), but yeah, we both really enjoy it.