Do you call it genocide when you step on an ant hill? But yes, generally speaking.
No, there is no evidence presented that the gods involved in the destruction of the crystal sphere were the FR gods. What is your obsession with making everything a FR god? Also, the destruction of the sun is ambiguous IIRC.
This is 100% true. And?
OK, that seems to be the case.
It appears from the text that gods no longer have any part of Fyreen and they are not worshipped. At this point they are probably a myth more than anything else. So I would say no, it does not "contend" with gods (genocidal or otherwise).
OK, that sounds correct. However, we don't know what will be unlocked on the DMsGuild until they tell us. It is possible that "defilers" may not be a part of it. It is also possible, though I doubt it, that they unlock Dark Sun in addition to Doomspace.
Absolutely. You can play a godless version of any D&D setting really. However, you cannot official convert Dark Sun yet. Doomspace =/= Dark Sun