What is the difference between the word "madhhab" (school of thought) and the word "fikr" (thought/ideology), and is it correct to say "the Salafi madhhab" or is "the Salafi fikr" more appropriate?

There is no contention in terminology, as both "madhhab" (school of thought) and "fikr" (thought/intellect) overlap in their connotations.

A madhhab is a method and a belief, or a set of related opinions and theories. As for fikr, it is the application of the intellect to what is known in order to reach what is unknown.

There is no objection to using the expression "the Salafi madhhab," and its usage has become widespread in the books of scholars.

"Islamic thought" is the body of sciences and knowledge based on Islamic principles, or the product of thinking committed to Islamic guidelines. "Salafi thought" is close to this.