Nice, but you are just forgetting that the timeline in the show is all over the place and is not right, so trying to use the timeline from the books to the movies is silly. By example, the word Uruk should not even be a thing yet, since the blackspeech is invented by Sauron later, and the word was used for the biger orcs in the third age..
Adar implies it is his children, like he is their father, biologically, so its not many generations, again, due to the timeline being compressed in the show and they changing up the lore.
Both races were corrupted and breed with each other to produce the orcs.The mixed Origin from what I've found is that both elves and men were corrupted not that they were mixed together, If orcs come form both elves then some orcs would still be elvish so that would still fit with Adar.
And again, no, it would not, because Adar do not share any of orcs characteristics that tolkien described.
that is only true because his son published silmarilion with the origin he chosed, is not Tolkien himself, by any means of canonicity, their origin is set unknown(and will stay forever unknown cause he died before finishing it) but strongly suggest human ancestry, because again, immortal orcs, and their twisted and corrupted souls going to Mando would be problematic for his universe.but again, repeated in both published and unpublished works it is stated that orcs are in fact Elvish they come from elves and other elves in the settings note that they seem like elves but savage and evil.
It was his later notes, mind you, the "timeline" put the elven origin as the early ones, that were scraped to give place to the one that they came from men, just because he died before he finished doesn't mean isn't as vallid(or more) than the others.Tolkein may have said in one note that they weren't elvish but in later notes changed again to them being elvish and in his published works both from him self and his son they are elvish.
I say they would look more like azog from the hobit or the ones in the show itself.Your right it doesn't guarantee they looked like them, it does how ever make it more likely that they looked like elves then the oatmeal orcs Jackson made.
Because tolkien description of orcs is again, smaller than men(only a few rare ones could stand to men height), thus way smaller than elves, jagged teeth, crooked, long arms, etc, not of that is "elvish"(so, yeah, Jacksons orcs are more orcs than Adar).
Is like looking at Gollum and saying "well this looks like hobit-ish that went to the dark and became savage, eating raw fish and living like an animal"(because he was) and Gollum is monstrous compared to a normal hobbit.
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The effects of the corruption would be show in their own bodies if that would be the case, see Gollum and how he changed after being corrupted. And they got Corrupted by Morgoth itself, not lowly ring. you know, the guy who made trolls and dragons.
The idea of they being corrupted and nothing changing just some marks on his face is nonsense.