1, It fits with the psychopath, because his intent is to continue forcing himself on her till he no longer enjoys it. The footage ensures she stays complacent while raping her.
2, the "Secret Gallery" isn't something that is in the games lore. It is the $100 tier photos he adds to the game at each update.
3, At the start of the game he willingly and without hesitation gives MC money, till he says MC should just do work to earn money instead.
4, You describe the MC. He doesn't think he can fail raping his teacher, but does.
And not all psychopaths kills. It comes down to "what would cause a greater problem". The husband knowing that the kid was at the apartment could finger him as the killer and he would be sent to jail. A psychopath would know this and work around it. The blackmail and recording is a much better option since it is part of "his game". He is in control with it.
still i find it humourous that you find sympathy for the sociopath, celia. yes she very clearly is one, as the mc may be as well. also i fail to see anything he did to her as rape, she could always say no. her desire to keep hidden her criminal activity overrides that.
so all he is really doing is receiving payment for not turning her in to law enforcement, so basically forced prostitution, but i don't think with celia's mentality that really bothers her. she desires total control over others and when she can't have it, she lashes out violently which is why she trains in martial arts. btw you left out how judy also has problems, more so than the mc, she is the one who talked him into all of this haha as any psychologist she is quite clearly insane. oh yes the footage, i really do not think the footage kept her on the table it was probably more due to the fact of the electro stimulator dildo, enough volts thru your body and your muscles no matter how big turn to mush and you can't move or can only barely move. but if you noticed, she likes his cock, she doesn't like him cumming inside of her because due to her sociopathic tendancies giving life to another is just something she will not do. which is why she hasn't ever had a kid before even with her husband.
if you really move back and look at everyone in the game as a whole you will quickly notice they all have some mental abberations as dictated by society at large. but are they really mental abberations or just ppl not being inhibited by societal rules?
i do believe tho that celia deserved some of the blackmailing for her part in the public humiliation of the kid. she could have just politely said no and moved on but instead she decided to make it public so all his peers would know. probably in the sad hopes of crushing him so much he would commit suicide so she could get off on that. one thing that does puzzle me tho, why are we pondering over the psychological aspects of fictional game characters? is this not yet another sign of mental abberations in ourselves?