Haven’t read every word in this thread, and you may have already addressed this, but as a registered professional land surveyor, I recommend a few other things to consider:
Does your county require permits for septic systems? Big problem here if you are caught with an unpermitted system. It may work flawlessly for decades, but that is irrelevant - if it doesn’t have the permit, “Ist verboten!”
Does the nearest municipality exercise “extra-territorial jurisdiction” over your area? In Texas, municipalities are allowed to extend the reach of their influence some statutory distance out from their corporate limits, depending on the population. For Waco (population 100K) the ETJ radius is 5 miles. Within that radius, any dividing of land has to comply with their subdivision ordinance.
Around here, if you have more than one septic system per tax parcel, you have to sign an affidavit that the system is for a “guest house” or some familial arrangement where no rent money changes hands.
If you sell someone a part of your land off the public road, with easement access only, our county REQUIRES you to build a 22’ wide asphalt road across the easement, and a 45’ radius cul-de-sac at the end of it has no outlet. The price for such a road can approach $100/linear foot built to the required standards.
Make sure you check for transmission line or petroleum pipeline easements that can routinely be 100-200’ wide.
Despite all that, homesteading is DEFINITELY a worthwhile endeavor, especially for someone your age, with plenty of life and energy left to make a decent run at it. We all know you ain’t afraid of work . . .