The one-dollar filing fee claim is not something we can verify, and it is worth being skeptical of. Court filing fees vary by county and state, and while some jurisdictions have reduced or waived fees for indigent filers, a flat one-dollar fee for a divorce filing is not a standard we are familiar with. It is possible someone heard about a fee waiver program and the details got simplified in the retelling.
Here is what is actually available and worth exploring.
Inmates can file for divorce pro se, meaning they represent themselves without an attorney. Many state court systems have self-help forms available specifically for uncontested divorces, and an uncontested divorce where both parties agree on the terms is significantly simpler and cheaper than a contested one. Since you have been separated since 2010 and both appear ready to move forward, an uncontested filing is the most realistic and affordable path.
Your husband can request the appropriate divorce forms through the facility's law library. Most correctional facilities are required to provide inmates with access to legal resources, and a self-help divorce packet is a standard request. He completes the paperwork, it gets filed with the court in the county where the marriage was established or where you currently reside, and the process moves from there.
From your end, Googling the specific divorce filing process for your county will surface the self-help forms and instructions. There will be a filing fee, typically ranging from one hundred to three hundred dollars, depending on the state, though fee waivers are available for those who qualify based on income. That waiver application is worth completing if finances are tight.
The courthouse clerk's office in your county can walk you through exactly what is needed without charging you anything for the conversation.