I am in the process of putting together a set list and will hopefully be ready in a year or so to start doing something.

I just can't seem to get through a song completely clean. A wrong chord, losing the rythem, or some other boo boo seems to plague every song.

Is there something you guys did or a way you practiced to help you get everything nice and clean?
And after that, more practice.

I know guys who practice 8 or more hours a day, when they're prepping to go into the studio or on tour. How long have you been playing?
Enjoy your playing, don't make it into a job. Meaning how ever much practice you can handle without totally hating playing you should do. Of course don't slack off either, I'd say atleast 30 minutes a day, make sure to slow down what your playing and get it perfect before speeding up.
This is problem most easily fixed by slowing down.

Never play a note until you are sure it is the correct note, and also that it will sound correctly.

You can slow down on easier parts and speed up on faster parts, somtimes that works, but really when you aren't playing with a metronome. A lot of classical guitarists do this.

Also, don't forget to relax..
Muscle memory

Every day is a Meshuggah Binge day
Perfect practice. Slow down enough that no matter what, you will play the correct notes and chords.
its the muscle memory of doing it perfectly that will help you not make mistakes.
I used to break the song in multiple small parts and practice every part until i got it perfectly than just put it all together. It worked very well for me