Well you can cheat with save editor, just be careful and it seems that the multiples of 5 are the numbers that count for scenes. Sis needs corruption 35 and if I am right you need to lend her to that asshole to be able to further up her love. (That is why I said I do not share in games like this, even if I am playing an asshole in a game like this I would still in no way let a guy like that cousin of landlady near my sister if I have any choice, even if she was not a LI in game.
Did not play latest version since I got there is only an extra NTR scene I am not interested in anyway, so not sure you can reach 50 love with her already. For the girl at work, go on dates with her and slowly raise both her corruption and love (if remember right love is at least till certain number do nothing(no bj at end, just let her go) with her at your home). At certain moment you will unlock her pussy, with love and anal with corruption.