Have you done a full wipe before install? And did you test the mic before or after you started installing/restoring apps and data?
About m2sd, yes it is flexible. You can type "m2sd help" in a terminal to get all available options. You can also read about them on the
m2sd thread
If you need space that bad, you can enable dalvik-cache and/or data to move both /data/dalvik-cache and /data/data to sd-ext.
# m2sd data enable (This might slow your phone down)
# m2sd dalvik enable
You could also revert the data and sd-ext partition.
1: m2sd rmount enable
2: m2sd data enable
3: m2sd apps disable
This will mount sdext on /data and data on /sd-ext. Then it will keep everything on the sdcard, except for /data/data which will stay on the original data partition do to speed.
This is the two best options to get more space.