What is supposed to happen, as near as I can tell:
The highest priority device available from the following list is used for playback:

1. 1/8" Analog
2. BT HSP
3. Built-in Speakers

(Which seems to match what you're seeing now.)

Recording is like:

• If playback is through BT, recording is also through BT.
• If playback is through 1/8" Analog, and a 4-pole connector (with mic) is used, recording is through the mic connection of the 1/8" jack.
• Otherwise, recording is through the built-in mic.

Of course, some apps, including the FM Radio, can demand playback through the speakers when a cable is connected to the 1/8" jack (for use as an antenna). I am not sure what effect this has; I know the FM Radio wrecks things, so I don't use it. Mediabox, I believe, can also switch outputs, but does not mess things up. I haven't tried it, so I'm not sure what it does, either. You can also wrangle support for A2DP (playback only), and I'm not sure what that does, either.