No prob.
Yes, and how they lose is an admittedly valiant and quasi-successful manner (wiping out the Black Order, almost overpowering Thanos) followed by complete and utter defeat.
No one in the audience cares about future events. This is mostly Marvel's fault for prepping you into thinking "oh I wonder what Thor Ragnarok is about" like 3 years before it comes out, and their platter of end-credits "ooooh look who's coming next year!", but the point of Infinity War is about what happens in Infinity War and before. People are sad because in Infinity War these heroes die in this way. Avengers 4 does not exist. Hell, movies, as a concept, are irrelevant, because Infinity War and the 10 years of MCU have them so immersed, that it's like people they know actually died.
And no, Tony dying wouldn't be more powerful--there's a reason why Peter Parker, young, teenage Spider-Man dying in Tony's arms, begging not to die as he's erased from existence is the biggest, saddest death scene, because he doesn't die like a hero, he dies like a kid. Tony dying like a hero is expected, in fact, because of the fact we had three Iron Man movies we thought he'd die anyway. But he doesn't. Everyone else dies. And now we get to see the first first Avenger handle something like that, which is much more impactful than pretty much tossing him aside. If he died here, he certainly isn't coming back later.
Since we didn't properly see him losing the first uncle, it's just rehashing what we already know about Peter Parker, and it won't really change anything about him. Frankly, let's not make Tony Stark anymore important to the Spider-Man mythos than he already is in the movies. He makes his suit, mentors him, etc.
They are paying attention. They don't care. Because they aren't watching Avengers 4, they're watching Infinity War, and again, they lose and die.
Do you really think they should do the "cut to black" bullshit, breaking the immersion, turning every conversation into "wait, what happened and who died?", and forcing Avengers 4 to waste time naming everyone who died, which if it's still going to play out the same means that Spider-Man, Black Panther, etc. still died and would be even less believable because we didn't see it, instead of getting to the point, so that the idea that the heroes come back isn't immediately obvious?
