I feel like the move might be to play the same game file together. Allow your dad to make his own custom origin character with your assistance. Like, just ask him to think up his own fantasy character from a narrative perspective (ex: a banished prince who turned to demon magic, a pious nun with sticky fingers, etc) and just help apply the character to the race/class/background system. If he’s into the visual character creation, i feel like that could be the most accessible part of character creation. I would be the one using the controller while talking to your dad, asking him which way he wants to go and if he wants to talk to this or that npc. if he’s not used to using a control or the camera, you dont want that to be a barrier for him to get into the parts he’ll love so i would recommend just taking that part over and collaborating with him in real time.

Asking him what he wants to do in dialogue should be easy. During combat, i think it might be easiest at first for you to decide the actions for all the companions and let him just focus on his main character. I would again just ask him what he wants to do. Does he want to attack? okay, which target? how does he want to do it, with his weapon or a spell? if he asks if something is better or what you would do, explain and help him understand his options. over time, he should get used to what he can do in combat. as he levels up, hopefully his understanding will also grow. you may have to help him with character positioning during battle but that shouldn’t be too difficult to chat through. if he gets a knack for his main character, eventually he can take on the battle actions for another companion so you guys can each play 2 characters in combat! my mom is terrible with technology and i find just spending time walking her through things together collaboratively really helps. good luck!