Travel between Schengen countries with an expired NIE

I'm from the USA, living in Spain, and waiting for a pareja de hecho to get through processing. I was originally here on a student visa, but my NIE expired at the end of December (shortly after I applied for the pareja de hecho).

The local office for parejas de hecho has made me order a new birth certificate from the US, so right now that's what we're waiting on. All the other documents are already submitted/approved.

In the meantime, I have a trip to Italy booked at the end of this month (during Semana Santa). I want to go, but I'm a bit worried about getting deported/fined crazy amounts of money if for some reason they do check our passports at the airport in either Spain or Italy, since technically I'm "between visas" at the moment.

I tried requesting an autorizaci?n de regreso from the local immigration office, but they told me that 1) they couldn't issue one when I don't have a NIE application processing (just the pareja de hecho), and 2) they wouldn't issue an autorizaci?n de regreso for travel between Schengen countries anyway -- just for travel outside the EU.

So far, the options I've thought of are the following:

1. Skip the trip -- easier to lose a fun holiday and a few hundred Euros than to get shut out of the country
2. Email every immigration authority I can find to try to get it in writing that I should be able to come back -- though I'm having trouble finding contact information for those authorities, of course
3. Pack the documents that say the pareja de hecho is processing when I go to Italy, and hope for the best

If you know of immigration authorities that can be contacted by email -- or you've traveled extensively between MAD and Milan or Venice and know they never check passports -- please leave a comment!

Thanks for your help.