TWO PART RANT: secrets and divorces

t
okay so lets make it quick: my dad has had issues with pornographic photos on his phone of playboy models and porn stars. my mom had found out back then and now that he locks his phone and no longer keeps it downstairs, there's something going on. so the day he bought his new truck, i got onto his phone to set up the wifi for his phone from the truck. well as i was going to setting i caught a glimpse of a playboy now app. 
now i know why he has passwords on EVERY app like messages and photos. should i tell my mother or no?
.
my dad is also annoyed at my mother because shes going back to her old ways by sleeping until 3pm, always on the laptop all night, and not taking her meds(depression pills, blood pressure and three other types of pills). (he gave her a chance to fix herself when he filed divorce papers with her and told her to go to a doctor and get a life back and listen to him without making up excuses or anything (since she wouldn't clean the house anymore or make dinner or even bathe) and she eventually did (and he cancelled papers) but is now going back to her old ways) according to my dad: I'm the only reason why he comes home and hes at his last straw with my mom and wants to file more divorce papers and end it. i want to talk to her this time but... i wanted help from dad and he said no because hes done trying to talk to her.