You're making the mistake of assuming evidence is only ever going to be evidence of one model. That just isn't the case; good FE models, like DET, respond to the objections you brought up (DET provides a variation beyond the uniplanar map, which answers most of your queries right off the bat.
How does that even make sense? Are you saying half the planet lives on a different plane?
The Sun's more complex, but just comes down to perspective
and the source of its light).
The sun isnt complex, it is only seems complex so that it can conform to flat earth models. There is no way a sun hovering above a flat earth can project light to the underside of clouds.
An observation RET explains, that FET does not, would be evidence.
I am sorry, but that is not evidence. That is just a round earth assertion that flat earth can not explain. Evidence would be photos, videos, scientific or mathematical calculations that disprove a flat earth could exist.
The problem is when REers assume 'RET explains this' means 'FET cannot' when there is no logical implication between the two, or when REers just refuse to learn models which do answer the questions.
Yet, this is exactly what flat earth believers do.