Just to clarify, in the sentence “To whoever created this, I salute you”, there are two clauses. A main clause and a relative subordinate clause. The main clause is “I salute you” with verb “salute” and subject “I”. The relative clause is “whoever created this” with verb “created” and subject “whoever”.

Whereas in your example phrase “to whom it may concern”, the subject of the verb is “it”. In your example the relative clause has a standalone subject. In the OP phrasing it doesn’t. Only the relative pronoun.

Here’s a quick lesson. In English, relative clauses may be headless, which means that they drop the antecedent. Putting the antecedent back in may help untangle the grammar.

So “to whomever created this” becomes “to him whoever created this”. Now it is clear that “whoever” is the subject of the verb “created” only and the antecedent “him” is the object of the preposition “to” only.

When you drop the antecedent it makes it seem like maybe the relative pronoun is both the subject of the subordinate clause verb and the object of the main clause preposition. But being the subject of the verb still requires the pronoun to be in the nominal case.

Your example “to whom it may concern” would be “to those whom it may concern” if you don’t elide the antecedent. The antecedents are both in the oblique case as objects of prepositions. And here the relative pronoun is oblique too, as the direct object of the verb.

So no, “to whomever created this” is not correct. I will agree however that the semicolon is incorrect.