FloorPus's journey

I recently accepted a job offer that I'm genuinely excited about, and now I'm contemplating how much notice to give at my current job. I've been working here for 2.5 years, and honestly, I haven't enjoyed it at all. This position was never meant to be permanent; I took it as a favor for a friend who needed a replacement. During my time here, I've seen four coworkers leave, with three providing at least two weeks' notice, although they didn't stick around until their last day. One even quit on the spot. My boss has a habit of talking negatively about everyone, blaming them for issues, regardless of whether they still work here. For the last six months, I've been the only employee in the office while my boss claims he's searching for new hires. I’ve taken on multiple roles, essentially managing things without the title or proper compensation. Given all this, I feel I have no reason to stay. I do have a somewhat decent relationship with my boss, and I know he needs time to find someone to take over since he lives out of state. I'm torn between giving a two-week or three-week notice. I don't plan on returning, but I also don't want to burn any bridges completely. I feel a little bad about leaving him in a tough spot. If you were in my situation, how much notice would you give?