I cannot say I know much of anything documented about Thomas and Maria's family.
Jay's lovely survey of Census and book sources is helpful, together with the very limited supply of Church records.
I have not seen anyone say they went to the County records looking for land and estate records, or specific documentation of tax assessments.For NY this is a bit easier a time than we had in PA, where there were several County changes in the 1770's-1820's period that required going to far-flung Courthouses.E.g., a Washburn mortgage recorded in Wayne Co., PA.
I hope you will find a way to get into the records to try to tease out some helpful data.
Be aware that NY County Courthouses can be less friendly than they were 10 or 15 years ago.They are very squeezed for resources.The Tioga Co., NY County Clerk's office began charging a $40 fee for entry to the records.Considering the treasures, that is not outrageous, but not everyone is prepared for it.
Inquiries to County and Town Historians can also be fruitful concerning what records are where, and suggestions on where to start.Nearly all of these people know their stuff and are happy to share their knowledge.Some are linked to via County sites.Contacts via snailmail should always include very specific questions, and a SASE.
The two golden words 'thank you' should be liberally strewn about, as well!This is not the sort of advice I would have given some years ago, but the rapaciousness of many present-day internet "researchers" (e.g., those demanding answers, who think they are doing research by asking others to do their work, who *never* thank those who come up with answers, or who react with anger at research tips instead of genealogy-on-a-platter) makes such little reminders needful.