The US does have more than 2 parties though. I think the argument being made is less about there being only 2 parties and more to do with how power is distributed. In a FPTP system, you will really only have 2 major parties that swap power around, even if a third party can attract a significant number of votes. That is essentially the main strength of FPTP, it almost always produces a dominant victor. In practice the Canadian system has seen power swap between the Conservatives and Liberals. In the UK power has swapped between the Conservatives and Labour. In India, power has swapped between the BJP and the INC. In Mexico there have only ever been 2 parties. I've tried to find more examples but unfortunately most countries with FPTP do not have good wikipedia pages for electoral results.
The US does seem to have a uniquely dysfunctional system, but I don't really see any significant evidence from other countries with FPTP of third parties being able to enact real change.
The Coalition government of 2010 was the first coalition in almost a century, and indeed you can find only 2 coalition governments in modern British political history. It was not the norm at all, and was heavily influenced by the bizarre regional nature of British politics. Meanwhile the most recent election can be seen as another FPTP aberration, since the most representative government would have been a Lab-Lib-SNP coalition rather than a Con minority. What is more, 2017 saw minor parties almost completely wiped out with 82% of votes and 89% of seats going to the 2 largest parties. The UK is a poor example of third party influence, I would say.
I do not know, but I will advise you that your query is likely to find more answers if you asked it at Overcoming Bias, as Hanson tends to respond to comments over there, or perhaps SSC, given the comments there have a decent number of economists who will be more familiar with those kinds of paper
The main flaw with the argument presented is that it makes a huge leap from 'Obama shows support for the One-China policy' to 'China uses this as evidence that it can do whatever it wants'.
The far greater change within China was the ascendance of Xi Jinping, not anything that America does (ironically, exactly what the user ends up suggesting you look at for Taiwan)
I don't really follow official statements from the US government, but can anyone who does say that the statement linked in the argument represents some major departure from US policy? Could it not simply be standard diplomacy talk? I think it's a major stretch to go from that statement to 'Obama's Pro-PRC policy'.
On 1, whilst that should reduce your belief that Trump himself will fire nuclear weapons, it is a fairly weak argument for several reasons: first, many many people have had something to protect yet engaged in reckless behaviour anyway with no regard for others. It's on a much smaller scale than starting a nuclear apocalypse but we should still consider that family members are only a weak protection, especially if, as others have argued, Trump is highly impulsive. Further, it only holds if Trump really does value his family highly, higher than his own self image, and given that he is a massive narcissist I'd say that's not guaranteed by any means.
The second issue is that there are more ways for MAD to occur than simply Trump ordering an attack. A nuclear war could be started by other nations, and there is reason to believe that Trump leads to a higher probability of this. First of all, he has encouraged nuclear proliferation, which will simply increase the number of actors capable of an attack and thus inevitably increasing the probability. Secondly, many non-nuclear nations may be tempted to acquire some if they believe they are undefended, which again is something that Trump has stated. Perhaps Japan feels endangered by North Korea and starts their own weapons program as the US pulls out troops or some such. I believe Scott Alexander made a similar argument over at SSC, probably better worded than mine.
I have no disagreements on point 2, and no comment on 4.
Regarding 3, I think this is a false argument. The issue I have is that 'Islam' is not a nation state or even a physical construct , you cannot start a nuclear war with 'Islam'. Presumably when you refer to Islam you are talking of the danger of a terrorist group or possibly ISIS. However, its difficult to see any MAD situation with such groups - for one, it is extremely unlikely that they are ever able to acquire more than one weapon and thus they can't 'retaliate' further. In addition, if they were able to succeed with a nuclear attack, there would also be nothing for the US or others to retaliate against. You cannot launch a nuclear strike against Al-Qaeda, and though ISIS do have land to attack they are now so spread out that it simply wouldn't make sense to go with a nuclear option over conventional warfare (albeit this can change over time).
Perhaps I'm misunderstanding the study that was performed, but from the articles it seems that this study has only been going on for 3 years now? In which case, any one sitting at the top of the heap is still pretty likely to have gotten there largely through luck. With a large sample size it's entirely possible for at least a couple of people to 'beat the odds' and get a number of questions correct again and again, without necessarily being any better than those who did poorly.
Even with a fairly significant number of questions being asked and rated, it does not appear to be a long enough study to start suggesting those at the top have better skills as opposed to better luck.
Indirectly, pressure from UKIP led to the current Brexit situation - which as gjm points out, has not yet resulted in the UK leaving. However, UKIP's vote increase didn't cause Brexit, it simply led to a referendum. But the conservatives could have easily not called the referendum in the end since UKIP's high vote share did not translate into any seats in government. I think it's much easier to pin the blame on Cameron's arrogance and putting party politics ahead of country, than it is on UKIP.
Nonetheless, even if you do not agree with that assessment, Brexit remains one data point. I am not personally aware of any other such events occuring in the likes of Canada or India, or similar examples in the UK.
I know little of the US pork barrel system, so can't offer comment on that.