I have a T as well who is exactly my father's age...

It was hard. It still is. I wouldn't have seen him by choice but was referred by my first T (female) who wanted me to see him because his modality is informed by bodywork, and my condition often manifests as debilitating pain.

It took over a year to really trust him. Sometimes it got ugly, I would panic and cry and scream and dissociate with him calmly reminding he was not my father. We did a lot of boundary exercises where he would stand closer or further away from me and I would describe how the different distances made me feel. For a while he just sat very far away from me, he would let me set up the chairs how I wanted.

Another thing we did was summon the part of my T (and the part of me) where the father was present, assign it to an object in the room, and yell at it and tell it to get out. After that I would hide it in a closet, put it outside, in the bathroom, whatever. He has a home practice and I sometimes wonder what his neighbors think.

In the end what helped me the most was that he repeatedly told me that he didn't want anything from me, and that I don't owe him anything. My parents were manipulative to the extreme so I always suspect an ulterior motive.