If you want to use your high gear I'd add two washers to the axle, one on either side (fairly thin) to space the gear out from the chainstays.

To be honest, your main problem just sounds like you need to dial in your drivetrain. I.E. check cable housings for kinks, bends with too sharp of turns etc, friction in general in the cabling... also since you say you're new I'll just name off some basics, like setting the high-low limits on your mechs is very important, as is the proper cable tension