Don't even worry about your speed. You are riding circles around the people on the sofa. My wife has been riding with me and her usual cruising speed has gone up from 6mph to 8mph over a few months.

I can suggest a few things, some of which have already been mentioned:

-Find alternate routes that avoid the worst traffic.
-Take the lane when you must.
-If you have no option but to take the lane for a short stretch of narrow road, do a "hold and release". Hold your palm out in the universal "please wait" indication. This lets the drivers know you are aware of them and are asking them to be patient. Once there is clearance to safely pass, move to the right and wave them on, giving them a friendly "thank you" wave as they pass.
-Use bright front and rear flashing lights during the day. My personal theory is that this makes the cyclist a larger object visually and drivers will instinctually give more clearance when passing. There has been some debate as to exactly why it works, but it does.
-Lurk in the safety & advocacy sub-forum for a lot of other threads with suggestions on this subject.