Something's gone wrong, and I'm not sure what to do. Think my dad is having an affair.

Copypasted from my post in r/family because I wasn't sure where to put this.

Going to start by explaining all out individual situations as best I can... not sure if I'm posting in the right place either. Should this maybe go on r/depression, or r/relationships? x.x;

I've been... moderately depressed for a long time, and stress definetly dosen't help between school (which I just finished- I am failing the job search so hard x.x) and home, with parents that... aren't the worst, by far, but it's still pretty stressful. I try to help out around the house now and again, but it's hard to get up the motivation.

My mom's situation is pretty similar to my own--Stress with work, then coming home to stress with dinner and family, and usually too down to get up any motivation to do anything about the ever-messier house. Also like me, pretty much her only social interaction outside of (school for me, at least up until a couple weeks ago)/(work), neither of which really count, is online. For her, facebook. For me, the handful of friends I've brought to my contact list over the years, and Steam. She's been getting pretty distraight over these past few days with what's been going on, and blaming herself, though not knowing exactly what she's blaming herself for. Another stresser is that all the house bills- groceries, gas, utilities, everything, even dad's own gas and cigarettes half the time, come from her paycheck, and it's usually not enough. Neither of us are sure where the heck dad's paycheck disappears to.

Now my dad... He's not around much. Every single day, he's always out until at least six, usually 8-9ish, and more than often enough 10-midnight. Sans weekends when he leaves a couple hours later from sleeping in, he's out of the house by 6 or so. Until semirecently, his time at home would be sleeping/watching TV/eating, plus the rare household chore that required something kept in his half of the garage, like a ladder or power tools. Sometimes I would have to go with him somewhere, and I'd end up having to sit in the car for a long time; playing slots at the gas station, or sitting outside some nondescript place, he usually paid me to not tell my mom where he was. There's also a couple pictures of seemingly random people I think we're somehow related to on his dash, where he used to have a kid photo of me-- mom dosen't like that, but hasn't spoken up about it. More recently, he had to get a Facebook for something work-related, and since then things have blown up. He got addcited to facebook games himself (slots, better than spending hours and hours at a real slot machine like he used to, I suppose), but the real problem is that he sees Mom being social on facebook, and (expecially with people that do shit like "kisses xoxoxoxox" and "Love you!" in general conversation with everybody) is super-paranoid about her having an internet affair- going so far as to, as of a few minutes ago, storming in and demanding all her Facebook and email passwords, as well as getting pissed and outright just leaving the house for a while/for the night after "catching" her sitting at the computer instead of sleeping or cleaning or cooking a couple times.

TL;DR: Mum and I are undiagnosed depressives who get our reccommended daily amount of social interaction through the internet, Dad's overreacting to mom's internet social life and thinking she's cheating, I think he's suspicious because he's probably cheating himself, things have started blowing up these past few days, and I don't know what the fuck to do, or if I can even help at all.

Even if he isn't having an affair, there's definitely something going on there as far as I can tell.

EDIT: After browsing mom's facebook and whatnot for a while, he's just now woken her up and said "You need to come out to the living room so we can have a little talk."