2. Back then, PRC was weak and still building up strength. Now PRC have some cards to play and won't give up traditional buffer NK to US that easily. It still wants to control NK therefore we'll have to see how far PRC will go to maintain that.
3. PRC cannot match exactly US weaponary but if maintain 1 generation behind, it will succeed. It won't fight a battle without preparing the battleground and conditions first. PRC may not win of US but in a war of attrition, it will force a settlement just like last time as both are Nuke countries.
4. Yes, I'm aware that US has gained much experience fighting small countries to improve their battle effectiveness and tactics but fighting against a large country in a limited scale, US hadn't won since the Korean War. Do you think US or PRC would go all out attacking one of the 5 big Nuke countries?
If PRC decided to fight US or US decided to attack PRC, they won't commit fully as they both don't want the war to escalate into something big (aka, Soviet Union & US). The result will be a cold war no matter what side wins or loses or both draws.