ProSeries will only use the address that in on the EFIN.

As you said, the IRS will not accept a P.O. Box for an EFIN.  However, there might be a work-around.  Some places, such as the UPS Store have 'real address' boxes that you may be able to use. (there are probably other similar businesses that do this). 

So you could get a 'real address' box, and use that for your EFIN. Then update the EFIN with Intuit and that address will show up on the tax returns.

https://www.theupsstore.com/mailboxes