I searched for county permits and there was never one pulled to create the 5th unit.

You dont need to have a permit for a legal size egress window.

Any new developments with your prospective tenant?

You should call as a prospective owner/customer and see what's standard in the marketplace. 

We do not allow self-tours through lockbox access, and even that may violate the "physical" prohibition since it would require prospective tenants to appear in person.

As you already know, NJ is very tenant-friendly, so be super cautious.We are on lockdown in PA, but we are still doing business:  virtual showings, and Zoom interview with prospects. 

They will bounce back in three months, but the strong buyers are taking advantage of the cheaper deals because they know this will not happen again for quite some time.As a buyer myself, I am avoiding houses that need many city permits involved with the rehabs.

I would suggest learn to market/prospect for your deals.

People are not looking to buy as evidence by your number of prospective buyers looking at your open house.So what do you do? 

Real estate is considered an essential service like banking and agents as well as appraisers and inspectors are permitted to continue to perform their jobs, of course with extreme care and caution to prevent infections.