Glad they addressed the age gap thing, while I get that it's not entirely out of place given the setting, just ignoring it would have been a bit off-putting. That said, I get the impression that Hades wasn't properly socialized growing up, and as a result has had his mental growth stunted a bit, he feels a bit more like he's got the mentality of like a 14 or 15 year old with his naivety and by the books thinking.
Also, Geralt's sister? She's totally the reincarnation of the Goddess of Love and Earth or something, she's locked up not because she's sick but because her powers (whether intentionally or not) drove her brother and possibly the rest of her family to be so madly in love with her that they refuse to let anyone else even see her. This is also why in the early flashback Hades has a grudge against her, in the future she or someone working for/with/alongside her will kill Rave, in furtherance of the war these two gods fight, which who the 'she' Hades referred to in regards to killing everyone related to 'her', it clearly isn't our MC here as he didn't really have anything against her specifically when she stood up against him. At least, that's my speculation.