Did you ever do a gauge for this? You probably should to ensure that you use the right sized needles.
Also, I think it's a shame that the instructor has y'all frogging everytime you make a mistake. There are videos on this site to help you. Find an experienced knitter to walk you through correcting your mistakes.
As far as number of projects OTN, I'm a one-project-at-a-time kind of gal. I find that I actually finish things this way. I can't stand to have things half-way done, plus I have some motivation to finish a project when I know what project I've got planned next.
Hang in there...you'll get it done...sooner or later.