We already know B is safe via IV if I am correct

We already know B is safe via IV if I am correct that in the ABSSSI trial B was introduced via IV.

If that is the case, what is the holdup to prescribe it as treatment for any respiratory problems associated with corona immediately should initial testing shows it does have a positive effect on corona?

As I see, it would not be hurting any patient and might/should actually save their lives rather than waiting for more testing. I know if I was in that condition I would plead for B IV regardless of whether it had not gone thru more strenuous testing if nothing else is available for treatment.

On one hand, we wring our hands as to a possible world tragedy but on the other hand we don't want to put anyone at risk prior to complete investigation thru lab trials.

You can't have it both ways. Pretty much the same as treating war injuries on the battlefield, you stop the blood flow with anything available regardless of whether it is sterile or not. Treat the immediate threat now and worry about results when they come to light. You will make some mistakes, but you will also save many lives that otherwise were toast.