Hi FEIRAB
I don't know the answer to your question, I am mostly aware that the curvature is something i have looked for and often seen absent. So this is a question way beyond what i ciould explain. But gravity is a huge issue of course - that is what supposedly makes the earth a sphere, and makes it orbit the sun.
One of thge solidest theories i know a bit about is that everthing is a live and consciousness is inherent in all things, and that it is sentimentalty and karma that keep things at the level they are at. All of the particles of a certain level have a conscious relationship with all of the other particles at that level. Also that gravity works something like train tracks - in flat lines(?) i believe... sorry not sure if i got this explanantion quite correct - it is more or less from the budhist teachings - i believe it is a good explanation.
I got that from the Falun Dafa(meditation/qigong/moral teachiing truth compassion tolerance) teachings, not form flat earth teachings, but thought i'd share anyway. The teacher of Falun Dafa says that gravity doesnot exist as do a lot of flat earth believers.