Yes SK was indeed poor...at that time Pak was doing comparatively well.
US patronage did help propel Japan/SK/Western European economies and that's one of the reasons why they are more or less strictly in US camp. China has NK to balance SK and to a much lesser degree Japan. For India, China has Pak on its side...and on the SCS side those nations are not strong enough to take on China...
But the long game that's being played is that together these small SCS nations combined with bigger players like US/Australia/India are increasing their efforts to check China. These nations were fragmented before and therefore not really a major threat but spearheaded by US, they are increasing their interoperability/cooperation. Though this process is going slow and the nations in this group have varying different ambitions/goals/political environments but I think within a few decades(as China rises further) they would synchronize enough to pose a credible threat.
Currently China should further try to win over Russia to its side even more. As far as the SCS potential threat is concerned even Vietnam and Phillipines could be worked with but it would require more of an effort. With these two nations along with winning over Indonesia/Malaysia, China can tame this SCS beast before it grows up to pose a threat. It would also be better for the region if things are worked out peacefully between these countries rather than it being a flashpoint that drags many nations into a war...and like u said, the more allies the more soft power.
It maybe 1v1 now but as it stands right now...I don't think there would be a war in SCS. At this moment China is content with its progress. China knows it's limits and is trying to build its power in terms of influence, economy and military. China would not take a step that would hamper this. On the other hand Japan, SK, Vietnam, Phillipines and other smaller players are not strong enough to take on China...US is not interested in taking on China alone bcuz it would be quite destructive to US economy and it may just end up as a Pyrrhic victory in the best case scenario.
So even in the event of a skirmish, the warring parties would be on a table to work it out rather quickly than going all in. Hence the chances of a full blown SCS war are currently low IMO.
In the future though it will be a different story. In the next few decades China would be stronger...better equipped with better tech...more able to take on other countries. On the other hand there would be more synchronized/combined threat from Vietnam/Phillipines/SK/Indonesia/Japan/Australia/US/India. US has been trying to get these nations to work together as a group. With more interoperability, holding exercises together, and having a common interest(opposing that of China's) would make this group a major credible threat. This is where there will be more of a chance of an actual prolonged war. Both sides would feel more confident/emboldened in their ability to take on the other and using force to secure their interests if they must. IMO that's when a war is more likely to break out and drag many countries into it.
, your generals are only good on paying tribute to China 
