I've learned that no matter how nice people seem, they can still fuck you over when money is involved.

Invested quite a lot of money and they chose to remove all contact with me after I told them I wouldn't bail out their debt.

So lesson learned. Absolutely make people accountable for their managerial actions every single day before they throw a business into debt. And get out if they show red flags of fucking up.

Don't stay at a shitty job just because you're scared of new things or because you think it's good pay. Put yourself out there and interview. Some interviews will suck, some job offers will be insultingly low, but eventually you'll find something better. And guess what? Maybe that one will end sooner than you'd like, but you're already practiced up and know how to interview and write a resume, so you can just dust yourself off and move on.

Also, if you get a huge pay raise, try to live at the same expense level as the old job. Maybe get a treat here and there, maybe fix that problem in your house or car you've been putting off, but don't blow all the extra money. Save some in case that new job ends and it takes a little longer to find more work than you'd like.