Adding more ventilation does not control humidity. Dehumidifiers and vapor barrier are vital to ensure high humidity is kept under control.
Mold and wood rot fungus in the crawl space can affect the living space. Make sure the mold remediation solution removes and disinfects.
Fiberglass insulation can be used in a vented or closed crawl space but there are better solutions available for your crawl space.
Addressing standing water from outside the crawl space can be difficult. Make sure you have a sump pump and trench just in case.
Older homes with less support can show their age with sagging floors. Installing floor supports is crucial to make sure your home is protected.
Closing the crawl space vents can allow soil gases to build up and enter the living space. Make sure to proper ventilate per EPA guidelines for encapsulation.