up until 2014 he simply would not be allowed to accrue cash of that amount. In 2014 a special type of account was created that did allow up to $100,000 to be gifted by other parties or otherwise saved but it is impossible for him to have legally saved $100,000 from his ssi income alone. If he saved every penny from a max monthly benefit of $771 for the 5 years since such accounts were created (which obviously is longer than the actual time in your scenario), he could have an absolute max of $58k and change. That would allow for $2000 (which is surely more than the actual amount allowable 5 years ago) of assets he could hold plus every penny in the ensuing 5 years based on the current max benefit of $771 per month.
You stated he saved the money from his benefits which means it was simply not legally possible to have $100,000 from his own income.
again, your claims simply do not line up with what is possible or even likely in the real world.
anyway, there really isn’t anything more that can be said. If you wish to contest the action of rescinding the deed delivered to you, you best get going. Time to initiate such a contest is limited if it hasn’t already expired. Even if you can argue the clock tolled due to you not being served properly, it started running Again once you became aware of the situation.
tick tock, tick tock