Self confidence is great, but it's a lot like hope: believing something can happen will only get you so far. If other factors don't fall in line, you're still not gonna succeed.
You both hit on a key point here: we don't actually know a whole lot about Sam's dad. All we know about the YEARS between leaving the Novas and his son's origin story is that he became a janitor. We don't know why. We also don't know why he drinks. Look at the pre-destruction shot of his bedroom again. The guy's obviously a little paranoid, keeping tabs on whatever info about alien visitation he can through the news. Plus, he took that recorder robot with him when he left.
Here's what I think happened: Sam's dad left the Novas, and went back to Earth, to hide/guard that recorder robot. They picked him because he was the only one with a family. He buried the robot in the desert, and became a family man. Lay low with a modest job that won't get him noticed, which works out especially well because there aren't very many job opportunities in the middle of nowhere in today's job market. Even still, he's constantly looking over his shoulder, because there are dangerous people out there who want that robot. As his family grows, he gets happier and happier, AND more and more nervous...the more time passes, the more he has to lose. He starts to obsess a little over news reports of alien activity, he saves news clippings, he makes a big chart on his wall, exc. He starts drinking to help deal with it. Just like his son, he's trapped in that little town...the difference being, it's the idea of that life ending that terrifies him. If the Novas want him back, he has to leave his family. If the badguys come calling, his family may die. And every day one of those DOESN'T happen is another day of paranoia and fear. I'll be extremely surprised if his sudden disappearance (and whole in the wall) isn't the result of big bad aliens showing up to take back that robot.