Grade I ankle sprain- 6months still in pain?

Altered dynamics of the sural nerve are common after ankle sprains. The "tingling" sensation you describe radiating through the foot may be such an indication. I would try to find a PT in your area who has taken a course in neruodynamics...it's likely an easy and simple solution that you might not have gotten in "traditional" physical therapy (ie, the range of motion and balance exercises). While the tradiational physical therapy is certainly important, the neurodynamics is often overlooked...then the nerve gets either adhered down or remains hypersensitive. I'd really see about getting back into PT with someone who can address this for you.