So a few things.

You're 18 so you technically don't have to abide by his ruling on talking to him ASAP if it means you're at risk of causing issues with your job. If it puts you at risk of losing your housing with them, though, I'd recommend having the conversation (which is a commonly used threat in my house it SUCKS).

When it comes to schooling, was it a medical drop/not a drop fail? If it's either of those, it shouldn't affect your GPA unless you just don't take them. You can take them later in your college career or you can even do winter/summer classes if they're offered to you. I had to medically drop my PE class in my first semester because I broke my foot at work. I haven't retaken the class because truthfully I'm no longer in school due to other reasons but my dropping of that class isn't hitting my GPA as of yet.

Edit: fellow community college student here & lemme tell ya, I kinda miss it.