Well, if you want to be technical about it: they are using Russian designs and got help from Russia.
Russian designs are also very reliable, which is why we use them ourselves.
Not at all. An important and telling detail: pintle injector is almost never used in Russia, but standard for Merlins. Or you can look into gas generator cycle, which isn't used for today's Russian kerosene engines except RD-107 family, which have separate components for turbopumps and pressurization.
Um, no, that's wrong. I'm thrilled for China's accomplishments and won't talk down about them, but your assessment of SpaceX is simply false.
The issue isn't so much ITAR, but tech transfer in general though. The US is an economic rival to China whereas Russia has roughly the GDP of NY. We've seen time and time again that feeding China technology only results in it being replicated and further developed domestically.
For the general tech transfer issue, did the embargo actually work? Look at supercomputers, satellites, nukes including its delivery systems and jet fighters etc. It didn't work very well to serve the US interests. It is a failed system that probably slowed we Chinese down a little bit, but in a long run it gives your rival all motivations to invest heavily in _all_ those areas and eventually master them. When the US is basically forcing its rival to invest in itself, it sounds like a strategic mistake to me.
As far as the trade imbalance, the things that would fall under ITAR (the only goods that are significantly restricted) are not particularly significant on a global trade scale. Yes, the US could sell a few billion dollars worth of F-22 jets to China, but that still wouldn't make a dent, and to acquire the tech, China would only have to buy one.
We're our own worst enemy.
You can't just jet off into interplanetary space and expect good things to happen, you need to develop a huge array of life support systems that need to be highly reliable.
The second is "thank God I'm not the head of security for SpaceX."