My four year old wore two STARband for 8 months (starting around 8 months) via Dr. Vicari and Children's Memorial. I cried like a baby the night before he got it, but cried even more when we had to get rid of it. We definitely saw HUGE IMPROVEMENTS with the shape of his head, as well as the symmetry of his features (if you look at pictures of him around 6 months, you can actually see how his eyes are not aligned).
He also had torticollis and we worked with a PT from 6 weeks until almost 3 years. You cannot notice a tilt at all now unless he's sick (and then, I'm the only one who can see it). I would definitely stick with stretches, homework, etc - anything your PT or OT suggests. We were very good about doing everything, but since his tort was so strong (he had negative range of motion when we started) and lasted for so long, we have had to deal with residual eye issues (strabismus, lazy eye, glasses since 2 1/2 and possible eye surgery).
Chase never developed a rash on his head - surprising since he has horrible eczema - but I would second whoever suggested dressing him in cooler clothes. He wore short sleeved shirts and jammies all winter long since his head would really be sweaty. I'd call your orthotist and ask their thoughts about the fit of the helmet.
Good luck! Hang in there.