1. The horizon line curves. It wouldn't if the earth was flat. -- Many parts of the 'earth' have broken away since it creation many thousands of years ago. We believe the landmass is shaped like a disc (the most natural shape in space, actually). But what you are talking about likely isn't due to the earth's pancakedness. Likely it is because of the natural atmospheric fogging that happens over considerably long distances (many miles on a very clear day). You'll notice that due to the way light works and atmospherics plays out that the fog leads you to see in a vast circle around yourself. That's a CIRCLE, not a SPHERE, proven by my view of the stars not being obstructed by these atmospheric effects.
2. If the earth was flat, I would be able to see farther than I do. Object moving away from me in the distance gradually fall below the horizon line, therefore, the world is curved, not flat. -- These are almost the same exact effects talked about on the previous point. Try again, please.
3. if the world is flat, and the sun is above it, then the earth would be lighted all at once, or not at all. People I personally trust, who live in different time zones than me have nightfall before me. Therefore, the earth is AT LEAST curved. -- Perhaps your mindset is stuck in the MYTH that the sun is **NINETY-THREE MILLION MILES** away. It is, in fact, barely several dozen miles away. Due to the natural (and DIRECTLY OBSERVABLE) dissipation of light at the rate of 1/d^2, it makes it ever more likely that flat-earth hypothesis is the RIGHT ONE. Round-earthers can't even explain this as well as flat-earthers, and yet they try to use it against us?
4. constellations shift as you move along the earth, therefore, it is at least curved. -- Yeah, and it works on a flat-earth, too. When the pancake is thousands of miles wide with stars only a few hundred miles above, it's quite easy and MUCH more reasonably understood. I'm sorry, but I can't take your word on stars being quadrillions of miles away. Maybe if you made some REASONABLE ARGUMENTS, I would be more interested in your belief system.