Do the above log files look even “normal” ?
It really sounds like one of several things. It sounds like you have multiple mt-daapds running (the multiple temp files in the db dir) and it’s slow because of db contention.
Or, you are cpu pegged on something else (or maybe on a transcode), adn that’s slowing you down. Transcoding will do that if you aren’t using the ivorbis-tools package, or if you are using a home-build alac decoder… not the alac-decoder package in unslung.