My set up does not involve a mac but I thought I could point you in the right direction for at least one of your questions. Check out this thread over at the flux forums. Echo is probably going to be your biggest challenged once you get the software side (ie bt connection etc) worked out. I struggled with echo for a long time and did a lot of research on software echo cancellation. At the end of it all the best solution hands downs was the phoenix soho card mentioned in that link. As you read through you'll notice the solution results in an external box enclosure which basically processes the audio to get rid of the echo. My solution uses the soho and the andrea mic.
Word of caution... don't complain about the price (as many do)... sometimes the best solutions come at a cost.