Perio does not answer my #'s: can teeth grinding of a moderate kind lead to bone loss? Why do I have bone loss when sulcus can be perio maintained?

Teeth grinding. The way your teeth hit together is very important, and if it's off a bit, and particularly if you are a grinder at night, the trauma can cause bone loss in an otherwise healthy mouth. Get a nightguard appliance from your dds and wear it.
Sometimes. Typically grinding itself does note lead to bone loss, grinding along with periodontal disease will speed the process of bone loss and possible loosen teeth prematurely. It is best to wear an occlusal guard at night, be conscious of grinding during the day, reduce stress or other mediating factors, and possible use medications if symptoms are severe enough. See your dentist, or TMJ specialist.
Difficult to Say. 1st, once bone is lost around the teeth it is difficult to impossible for it to come back. Our treatment goals at present normally focus on keeping what you have. Severe grinding could, i suppose lead to bone some degree of bone loss but gringin generally wears the teeth & the joints, not the supporting bone for the teeth. Maintaining the sulcus will not grow bone back - just prevent further loss.