It might have been true that the Bill of Rights at one time protected the individual from abuses by the Federal government only, the 14th Amendment changed things. With its due process clause and especially its equal protection clause, the protections afforded the individual against the federal government were then applied against state intrusions.
Additionally, when you say, that the constitution was intended to spell out the precise and narrow limits of federal power, I only agree to a certain extent. There are a number of clauses contained in the Constitutiion and its amendments that are inherently vague. Prime examples are the ability of Congress to "regluate commerce among the States", "unreasonable searches and seizures", "due process of law" and even "equal protection of law" None of these clauses are precise, perhaps intentionally so. An argument that these clauses should be strictly construed begs the question...why? The founding fathers, as well as any subsequent Congress could have further defined these vague clauses through constitutional amendment but have not done so.
Thus, they must be judicially defined, and that definition may change or may be applied differently over time as circumstances may require. For instance, as bright as our founding fathers were, do you think they could have envisioned a world with super secret electronic eavesdropping. As such, a definition of what constitutes an "unreasonable search and seizure" may necessarily be changed, or at least revisited.