Hello!!
My thoughts on your questions...
1) How important do you feel honesty is in BDSM relationships?
It is the building blocks of any fulfilling relationship.
2) How important do you feel trust is in BDSM relationships?
Trust needs to be earned in any relationship but in BDSM it is vital for safe play, IMO
3) What constitues cheating in a BDSM relationship?
Doing anything outside of a relationship that has not been validated by the people involved... anything that would hurt the other partner... do unto others and all that jazz.