The problem with the echo is one that can be solved with a noise cancelling solution such as the Phoenix MT107 device which works with your sound card to cancel the echo. This can't be done with our current software solution (BlueSoleil). The only way to do it without this hardware is to find a nice balance between the PC mic volume vs the speaker output volume. Meaning turn your mic volume (and boost) down until they can still hear you, then turn your speaker down until you can still hear the caller. 

Try the noise-cancelling hardware recommended here: 
http://www.centrafuse.com/SupportedHardware.aspx#mics

Here's a thread that discusses what it does exactly. There also is a visual diagram there to illustrate how its typically configured:
http://forums.fluxmedia.net/carpc-related-car-audio/11491-phoenix-audio-mt107a-hard-ware-echo-cancellation-noise-reduction-usb.html