Or could this more be an issue with their screening processes? 

I just sent a connection request so we can get into the details via messenger/phone.

It always makes me chuckle when an amateur Landlord assumes they know more about screening applications than a professional, trained property manager that conducts hundreds or thousands of screenings a year.A lot of the fees you mention are normal but you should shop around.

How about a phone call for the PM fees that they already charge? 

Now I am looking to figure out how to best screen my tenants early so I would have the lowest amount of vacancy as possible.

Great contractors are typically busy people and a knowledgeable HVAC Tech can absolutely give you an estimate over the phone.

Also, remember STR's are a hospitality business, so be prepared to chat with guest on the phone, text with them and make them feel welcome.

The O65 makes it almost nothing and the disability makes it nothing.If they don't list the non-exempted tax bill on the site, pick up the phone and call them.

The other issue is that you are unable to dictate who pays for the online tenant screening... now the applicants should always be paying for their own screening but think in terms of applicants wanting to fill your application during the showing and pay for the screening right then and there. 

Make sure all of the window screens are in good repair.