ctreyn,
While you could continue doing it yourself, I would think working through a landman would be your best bet, and depending on the complexity of the title, heirship, etc., possibly an attorney for curing the title. Both options will not be cheap. A landman’s day rate would likely be in the $400-$500/day range, and an attorney would bill hourly. You can get creative and possibly find someone willing to do the work for a contingency fee or something similar. In the case of selling the interests, a buyer will (and should) bear the cost of landwork. The catch here, in my mind, would be that you are not certain what the ballpark ownership interest is, and so it may or may not be “worth it” if too small.
It does seem like you have done a lot of leg work, and that would be very helpful to anyone working on cleaning the title up. One thought would be to pay a landman for a day or two to at least identify the acreage in those counties, and then assess whether or not you would like to continue with the title from there, or pick it up again later.
I cannot speak to the probate without having seen it, but a will need not specifically mention the properties in order for title to pass without an issue. As always, ownership is very fact specific, but what you describe does not seem too alarming or unsolvable; it just may take tenacity and money to fix.