Good luck. I adopted an older cat once, not long after my son was born. This cat never warmed up, stopped using the little box because he had to leave the room he was hiding in to use it, and eventually I had to return him, especially since he had chosen to hide in my son’s room and was using his clothes, etc for bathroom facilities.
Which was sad, since he was gorgous, but had obviously been left in a cage for too long and was unable to adapt to life outside of one. He’d been cagebound for about 6 months.
I hope your little cat warms up soon, and that he was socialized enough while he was waiting to be adopted. Sadly my cat had not been.
Kyrin