You old employer will not be able to completely stop you from making a living in your field. In fact the more restrictive the non compete is the less likely a Judge will be inclined to honor it.
Can you post the non compete agreement (just sanitize the names on it). I have heard of a Judge who allowed the ex employer to pick a very limited area (NOT New England, but maybe Boston proper) this leaves many other territories available for a Sales Rep to work. Or another Judge told the ex employer to pick certain accounts that they wanted the rep to stay out of. The Judge cautioned the ex employer NOT to give him too large of a list.
I would get a second legal opinion from a lawyer who specializes in employment issues or contract law.
You could consider writing a letter to your ex employer stating that you intend to honor the spirit of the non-compete and you will not actively pursue any of their customer base. But you do intend to work in the industry in an area where you have not predominately sold before. Do not tell them the name of a specific dealer. Ask them if they will agree to this plan. If they don't their unreasonable enforcement of the non compete will way heavily in your favor in court.
One Judge told an ex employer that they could continue to pay their ex employee NOT to work if they truly didn't want him to work in his industry. The ex employer became very reasonable after that.
Finally, have you spoken to the labor board of your state? If your ex employer dose not agree to your reasonable request file a complaint with your labor board. I am not sure that they will get involved in the non compete but you could file a complaint that you were unfairly terminated. Possibly even have the other reps join in, or jointly hire a lawyer. I assume that they are all in the same boat.
It is possible that the fact the compensation you were promised when you signed the non compete changed you may have some grounds there. But even if that doesn't turn out to be so, your ex employer can NOT completely stop you from making a living in your field. A judge won't allow it.
I wish you well!
Vince