@Howard Barrett hi, I am British/American (Birmingham to Denver in '93), but now I am in Coimbra. My American girlfriend and I, have been here for about a year and looking for our first Portuguese house hack similar to what you have done. We have prior experience with 12 properties in Colorado (that we still own), some of which are rented by-the-room. However we are not renting them to students. Have you considered renting to older tenants?
Lisbon/Porto/Denver share a similar affordability problem, and single people working in the city have a huge issue finding reasonable accommodation. We have found that renting to this older group leads to less problems, better income stability, higher profits, and easy lease renewals. The tenants tend to be stable long-term since they cannot find as good a deal elsewhere.
For our Denver properties we have set them up with nicer furnishings than you would for students, but similar services - we pay for internet/TV & utilities then offer the rooms as "all in" with no squabbling over who pays the bill. This will change your tax category from B (STR) to F (LTR).
If you have the option to re-finance then I would take as much cash out as possible for a new investment. I am guessing that this property will still be cash positive, but maybe only just. That's OK, it should also be stable since you may only have one or perhaps two rooms that are vacant at any time.
Also who are you using for mortgages? How investor friendly are they? Will they cash-out re-fi after a refurb / appreciation?
Let me know if you want to meet for a chat, I am probably going to be in Porto for the weekend of Aug 1st.
-- Mark