I know what you mean about the BG speed thing, it's a challenge. I set all my practice tracks at 200bpm and find now after several months that doesn't seem that fast anymore. I have pushed past a little but as soon as it gets sloppy I back up.
I know you need to gradually build it up, pushing does no good, just slow and steady. then suddenly it comes on, weird how it works.
Although some of the mega pickers play at speeds that are unreal, sometimes I think the melody gets a little lost sometimes. JMO