No vocals yet http://soundcloud.com/gabrielbacon/hey-lani

My setup is an SM-57 plugged into a DMP3 plugged into an old gaming sound card. Heavy moving blankets covering most of the walls in a 10x10 room 8' ceiling. Using Reaper.

Three questions,

1 - There is a persistent hum / rumble whenever I hit certain notes, you can hear in the guitar on this track. I can't figure out what's causing it. I've tried different mic positioning & playing around with the gain to no avail.

2 - Track sounds quiet, have to crank the volume even though it remains just under 0db. I'm thinking this is just because of the poor recording but not sure. Maybe in the way the song is crafted?

3 - When I render it to mp3 in reaper it comes out at over 45megs, what gives?

thanks in advance
old gaming card may have something to do with it.i used to have a bc rich bitch that hummed the guitar doc said the pickups were shorting out somehow so i had him replace the bridge humbucker with used duncans and it made a huge difference.could be the mic also are the notes that you hit that cause the humm low?