The DB8 is a good choice... I think there are even better options available.
I would not combine the TV and FM systems. Strong FM signals can interfere with TV signals especially if you need to use a preamplifier or distribution amplifier. If the HD-6000 is serving well as an FM antenna now, I'd leave it as is.
Reception of the Sutro Tower signals on the other side of the hills/mountains to your west, will require a highly directional antenna that also has high gain. It also needs to cover both UHF and VHF frequencies.
I would opt for a large combination antenna such as the Winegard HD7698P or, an Antennas Direct 91XG paired with an Antennacraft Y10713 using a UVSJ combiner. In either case, I would place an Antennas Direct CPA-19 preamp at the output of the antenna or combiner.
Rotating the antenna is an option, there are other options to consider. On a related note, consider opting for an HD capable converter box such as the
CM-7001. It could be useful even if you upgrade your SD TV set at a future date.
http://forum.tvfool.com/showthread.php?t=2882
http://forum.tvfool.com/showthread.php?t=820
If you opt to rotate consider the NTE U-106 combined with the NTE TB-105 thrust bearing.
http://www.3starinc.com/antenna_rotors.html