Congrats on your progress!
"What now?" I would hit Google Books and look for a county history of Wyoming County, NY, as well as town histories for its constituent towns. Most 19th century works of this sort contain biographies of "distinguished citizens." Ditto for George's point of arrival in Illinois. Of course, this assumes George was affluent and "distinguished" enough to get himself profiled. This also assumes that any such work you find is indexed. And if George was a humble tradesman of more or less common semi-anonymity, he may not be mentioned at all — most "ordinary" residents weren't.
You've looked for deeds, a will, probate papers? Any of these might name relatives. If George fought in the Civil War, military records might give his home town. As I think I suggested earlier, you just keep clawing at the brick wall in hopes of penetrating it somewhere.
Extensive data exists for one prominent Brooks family of Wyoming County whose patriarch, Benedict Brooks, was born in 1779 and had children in the right time period. Unfortunately, no George is listed between his children Grace (1820) and Henrietta (1822). We do have a 67-marker y-DNA profile for this line. The information I have on Benedict is too detailed to paste into a small box on this message board. If interested, please email me — trib AT tributaries DOT us — and I will send it to you privately. Can also discuss whether you might be a candidate for y-DNA testing.