Seems like you're just falling for partisan media histrionics and conflating a lot of different things out of context.

On Fox News, Trump said that regarding Muslims in the US, he would do "unthinkable" things, "and certain things will be done that we never thought would happen in this country".

In context, Trump is giving a tough-sounding but vague and non-committal response to questions about whether there should be a digital database of Muslims in the country. He later partially walked this back, saying it was a leading question from a reporter and he meant we should have terrorism watch lists. Which obviously already exist.

I've read Cory Doctorow's Little Brother, and this might be a generalization from fictional evidence, but I can't help asking: As a foreign student in the US, how likely is Trump to have me tortured for no reason?

I'd say it's about as likely as you giving yourself a heart attack reading political outrage porn.