One additional thing to take into consideration are the results of all the conversions. @smooth mentioned the HIVE to HBD conversions, and their associated 5% burn. In addition to this, I think the HBD to HIVE conversions also have to be taken into account in terms of how much is going in and coming out of the conversion, since if you convert 0.95 HBD to $1 worth of HIVE, then in essence the HIVE supply has increased, hasn't it? So we have to factor in any additionally created HIVE.
However, even if there is dilution of HIVE, this may be totally fine since in this special case all the newly-created HIVE would go to the DHF. But it's still important to account for all the conversions (amounts going in and going out) so we know exactly what is happening and what the outcomes are of the economic operations.
All the conversions are accounted.
No. Each HBD represents $1 worth of HIVE regardless of its trading price. These conversions don't increase supply.