Please help with 4 questions

Could you please tell me how a native speaker would write this?

1 I didn’t see myself get/getting fat. I put on 20Kg over the last 4 years. I didn’t realize it. (How would you phrase? Would you change it?)

Could you say that it’s a “small world” in this context? Is world correct?

2 It’s a small word. Everyone knows each other in the comic world.

How would you have phrased this? Is it correct to say half in half out?

3 I drove by a dumpster and saw a poster half in half out flailing in the wind.

Is this correct? Is it correct to say based on discrimination or discriminatory?

The stores reserve the right to deny access to people. As long as it is not discriminatory based/based on discriminatory/discrimination, it's fine.

Thank you very much