This is probably not the answer you were looking for but take it from someone who went through all of the same problems and then some as you are describing. My solution... GET RID OF THE MOTOROLA HEADSET! I had the HS820 and the HS850. I couldn't get either of them to work as I had hoped they would. I tried the new Jabra 800 and found it was incompatible with the TREO 650. I decided to do a little research on-line instead of asking the employees at Verizon and Circuit City to suggest a good option.
I found a headset by a company called Tekkeon. They have a headset called The EZ Talker Mini. I was a little sceptical as I had never heard of them. After reading many glowing reviews I decided to give it a try. What a difference!! For one, I can hear all of my calls without haveing the headset volume turned as loud as possible and still straining to hear anyone! When I make a call, the headset automatically engages. This never happened with either Motorola headset. It is lighter and easier to fit on the ear. It really is a great headset. I have not set up voice dialing yet as I wanted to make sure I was going to keep the 650 before I paid for the software for voice dialing but I spoke to Tekkeon customer support and they said they have heard fro customers that it works fine. Here is a link to the headset.
http://www.tekkeon.com/site/products-headsets.php
I purchased mine from ecost.com. I don't have the receipt in front of me but I believe it was less than $60 with shipping.
Hope it helps...