Re: The US Constitution isn't for personal interpretation.
Neither of those statements are correct. Taking them out of order:
"Tik-Toc's main argument seems to be that their servers in the US are too deeply intertwined with the one's in China."
They said nothing of the kind. Their main argument is "that's not legal". Their secondary argument is "splitting this up isn't feasible this quickly". Their tertiary argument is "you can't just split one piece of software into U.S. and non-U.S. versions, no matter where the servers are, because they're still one piece of software working on a global set of content".
"Which means they are implying that their CEO committed perjury before Congress."
The testimony concerned wouldn't even conflict with what you say they're saying. They testified that they have Americans working with American data on American servers without the Chinese employees accessing or using it. That's it. I'm not sure I entirely believe that, but nothing in that conflicts with having a single global network which isn't easy to partition on a whim.
"Congress is setting domestic ownership requirements as they do, for example, for US nuclear weapons makers."
Their ability to do that is limited. Yes, there are some areas where they have that power. Nuclear weapons are a bad example, since the government is the only place buying them so they can set whatever restrictions they want. Radio and television stations might be a better example as they are also forbidden to be foreign owned (sort of). However, they do not have the legal authority to impose that regulation on anything they like whenever they like. I am not a lawyer, but I think you have overestimated how clear this case is.