I got the motor back together yesterday and powered it up. Now it spins the right direction, so that's a good thing! It also seems to spin a bit faster than before (going by the pitch of the sound it makes). I don't know if this is because the battery cart was low on charge the first time I powered the motor (we use it to jump start Peterbilts) or if my brush timing is a bit off. The speeds seem to be very close, so I will leave it for now. You can hear the difference in the before and after videos.
Before:
After rotation and brush timing change:
The second one is much louder because the motor is running with the brush end up, as opposed to down in the first video.