It gives us credit score, Rental payment history, Landlord-tenant history, and criminal history. 

And tying them up in a 6 month contract is criminal in those scenarios.

Three of the 12 did not provide a bid and will be charged criminally at a later date. 

You can check the Franklin County court records for any evictions or criminal background and cross reference this with what was on the application and their credit. 

Do I move forward with them filling out the application before I've even closed on the property, along with paying for the credit/criminal/background check and sending them the Estoppel Certificate?

Credit score is great, no criminal background seen, no evictions, not a registered sex offender.  

You need to be researching civil not criminal codes.

Of course, we also need to complete background checks on each tenant, including criminal, credit, and eviction checks, and a solid lease agreement too.

For example, I mention that every adult must pay a $30 application fee, pass my credit/criminal background, make a combined income of 3x the rent, and whether or not the property accepts pets.

no one has mentioned it but Real estate agents can be targets of criminals and sexual assault.