From my own testing. Masturbation only will add a point up 6 lust. For some stupid reason the game seems too check your total lust score for the masturbation scene and adds 1 if its 5 or less. No other scenes seems to do this and will add point(s) regardless of your total lust score. (You'll have to do masturbation scene first 6 times if you want the highest possible points)
Incidentally this means the very first point you can get in the game is useless. The creators should change the masturbation scene to check how many time the event has been activated and stop awarding points once the scene has been plays X times. The creator should also add choice to skip a scene that already been view before points are given.
when you arrive in prison (undress for the guard +1), once in the cell "go get a job", then take the interview in the courtyard, once you reach the score of 7 (i.e. after a few days) return at the employment center to become a nurse this allows you to exceed 10 lust points, then for those who are stuck at 57 you just need to do the shower scenes, the card player in the rest room and finally the blowjob scene in the courtyard toilet... this will take you quite quickly to 107 points and without having completed the routes.
make the first phone call to initiate a visit from your boyfriend revealing that he has dug up things and that you have to look for a girl in the prison (she is in the back yard at 8 p.m.)
you can complete all the events in the infirmary this will not make you finish the game, porn route, prison boss, accept your fate.
the others are amuse bouche, the most delicate scene to do is that of the prisoner masturbating on one of your porn films that you have made (if too much lust does not trigger it)