You cannot use logic in metalogic to justify logic. Logic simply cannot be justified. It can be reasoned about, but there is no kind of reasoning about it that can validate, verify or strengthen it. And that kind of reasoning is not metalogic. It is just straightforward epistemology.
In fact, there are examples like Steven Kleene, who did both. He did significant metalogical work in a classical sense and proposed philosophically that our current practices in mathematical logic should be changed significantly. He was an intuitionist, but he also took part in metamathematical research of the ordinary variety. If the point of metalogic was to somehow justify logic, that would not just be circular, it would be a contradiction.
Verifying human logic is not what metalogic does.
Metalogic investigates what alternatives
for the ordinary rules of logic might work, what happens if you trade out one rule for another, for instance.
Model theory and category theory imagine smaller models of sets of axioms than the entire world of application that are selected to reproduce as many of the same combinations and processes as possible that are actually related directly to the rules and are not spurious additions from experience. Then it studies the relationships between those objects.
Other approaches to metalogic study the process of proof the way one would debug an algorithm. The intention is not to justify the proofs, but to see if there are techniques that we are used to, that do not accomplish the same things in different environments.
The question is always, what would happen if things were slightly different, slightly simpler, or slightly more complex than ordinary cases. It is not to justify current practices. We get results like Goedel's theorem out of metalogic by looking at a significantly simplified case, not at ordinary logic. It makes no attempt to prove our logic correct, though there is a step that proves that we largely get what we expect out of the formalism with which the rest of the proof is going to proceed.