In summary, the rules have to be this way because the alternative is guys being forced to play through/ignore the whistle in case it is reviewable, which would lead to more late hits/injuries. It's rough, but we live in an era in the NFL where judgement calls are being questioned like they have never been before, and some of them will never be reviewable. (But some like certain penalties definitely should...)
Basically, yes. The only exception in which a play blown dead can have its result reversed is the Hochulli Rule, that says that, if a play was considered a fumble after review, and there was a clear recovery by the opposing team, the team can keep the possession. If there was a player nearby and he didn't jump onto the ball, even if he were the only player close to the ball, it is not considered recovered, so all the players now get instructed that, should they see a lose ball, they have to try and secure it, just in case they rule it a fumble.
Regarding penalty challenging, I do believe decisive penalties should be reviewable. Like every team has an extra challenge per game to challenge a specific play. Not all penalties should be reviewable though. I think it would be boiled down to a penalty that nullifies a first down/score by the offense or that gives an automatic first down, in case the defense does it. Talking about that, I hate the fact that defensive holding is an automatic first down. It's just ridiculous. There was a play in a Broncos game that was a 3rd and 28, after back to back sacks, and then a holding call made it a first and ten 13 full yards behind the original line of scrimmage.It's not a loss of down on the offense, it gives the Offense the opportunity to repeat the down, even if 10 yards backwards. Just make it a 10 yard call on the defense as well. In most situations, it'll keep being as is, an automatic first down, but in cases the offense had a penalty or the defense did a great job on previous downs, the effort isn't nullified by judgment call.
I think Derek Carr is a bit too overhyped right now
Some people have him in the MVP conversation which is crazy.
Some people are calling Dak the MVP, even though he's been having enough time to brew tea before throwing the pigskin before that O-Line of his. Carr is the same. He's behind a great OL. But yesterday's game showed several flaws of his game.