Obviously bombs can run out. But that's why major NATO countries have stockpiles of bombs and the ability to produce them. The fact that they didn't maintain large scale artillery shell production isn't relevant to whether they maintained bomb production. I would guess that European NATO could maintain air superiority. The Ukrainians seem to have denied Russia air superiority without the benefit of anywhere near as large an air force.

Russia has been importing soldiers from third-party countries. It does not speak well for the state of your armed forces if every growing percentages of your troops aren't even your own citizens.

Meanwhile, Russia's economy has been collapsing over the past two years. Their central bank has a 21% interest rate, there a million jobs they cannot fill because those people are off fighting a war (it may only be 500,000 jobs, accounts differ). It's backstopped by being a petrostate so they have oil money as a country, but that only papers over things for so long.

Like I said, we've heard "Russia's economy is collapsing" for 3 years straight now. I even believed it myself for the first year, but I have relatives actually living there - who aren't even pro-war - and the picture painted in the Western press has little to do with realities on the ground. Right now the economy is booming as far as most people are concerned. How sustainable it all is, is a good question, but given that the same people making the doom and gloom predictions long ago, I don't see why I should continue listening to them.

As far as Ukraine being able to deny Russian air superiority, that is evidence towards my point that Russia would similarly be able to deny air superiority to any European force. Westerners are way too used to fighting colonial wars against people whose best AA weapon is an old Stinger, but these things work very differently against a more or less modern power.

The lack of manpower is, again, for political reasons. Mobilization wouldn't be any more popular in Russia than it is in Ukraine. So they want to avoid it if they can by hiring mercs as replacement troops, whether from the heretofore neglected Russian province or from abroad like with NK forces. But make no mistake, Russia can do mobilization if it needs to, and they have more enforcement mechanisms for it compared to Ukraine, not to mention larger reserves. This is partly why the higher-ups are okay with such high losses, and it takes truly massive screw-ups for generals to get kicked out - the government doesn't see those losses as unsustainable.