I consider you're talking about your employers, aren't you? As far as I know H1B can be extended to 5 years at max (2+2+1), so you should better hurry up. Propose them to share the costs of legal process if it will make them move up. I doubt you will have fun extending your advance parole and work authorization every year while waiting for your EBGC.

Keep in mind that there are some restrictions on owning the company which brought you on H1B and which sponsored EBGC for you. If your lawyer doesn't know anything about that, fire him and find another one.