I am in Santiago de Compostela! And I got a compostela!
Everything worked out in the end (of course...). As
@mspath suggested I asked the proprietor at the Casa rurale Parada de Francos, where I was in fact staying, for help, and he confirmed that I could pay the taxi with card instead of cash. With that worry relieved, I headed for dinner at the restaurant at the casa rurale. I had a table of my own, but ended up in conversation with three other pilgrims the next table over, so in the end I ended up joining them! I had a most excellent meal (I HIGHLY recommend this accomodation for the food alone!!), with great wine and even greater company. The fun thing was that although we were all on the same Camino, we each did it differently - I was a firsttimer, another was on his third Camino, and the two others were firsttimers who did it on bike! So that was great to exchange experiences.
The owner of the casa rurale (Pepe) had arranged a taxi for me for 10AM this morning. I was in Santiago at about 10:30, being dropped off at the bus station. From there it was just under 2km to the Cathedral. I did get lost! In fact, apparently Google send me down a route that's not part of the Camino, so weirdly I saw no waymarkers at all, and I even had a hard time getting my final two stamps for the credential - at one point I almost started wondering whether I was even in SdC at all.
I ended up getting one at the tourist info, and two at the post office near the cathedral.
I reached the cathedral at about 11:45AM. I weirdly didn't feel much of anything, except tired! Perhaps because I was alone, so I couldn't really share this moment with anyone else. But it didn't really feel like I had reached the end of a momentous accomplishment, if that makes sense. I did do the obligatory photoshoot - I took photos for two ladies and they returned the favor.
Next I headed to the pilgrim's office. It was busy, and getting the QR code was a pain, plus I really do feel like they don't explain it well enough. It was just a guy pointing at a sign going "scan the QR code!" It was a good thing I'd read on this forum what to expect. On the other hand, being able to check my spot in the queue onlline was very useful. I ended up having to wait about 2 hours, but this way I could spend most of it souvenir shopping!
And yes, I got the Compostela! They do check the credential somewhat thoroughly, which was on the one hand a relief ("at least I didn't collect all those stamps for nothing") but on the other hand a bit nervewracking ("will they notice I only got one stamp on the 25th? And that I got most of them at my accomodation at the end of the day?"). But I passed muster.
I got my final stamps, including the one that said I finished my Camino, then got handed my Credential! I bought a tube to carry it in, and then I was done.
I spend the rest of the day wandering around, visiting the cathedral etc. I had planned to attend the pilgrim's mass, mostly to hear me being counted as a pilgrim from the Netherlands, but in the end I was too tired and the weather was too bad to wait til 7:30PM, especially considering it's a 20 minute walk up AND downhill from the cathedral to my hotel. So I skipped it. Might do it tomorrow, or on Monday. Right now my plans for tomorrow are to do laundry, visit the pilgrim museum, and most of all to SLEEP IN UNTIL NOON.
Thank you all so much for your cheerleading and comforting words in this topic! It definitely helped calm down some of my worry. In the end I did the Camino my way, which was not the way I expected but, well, it is what it is. Will I ever do another Camino? I'm honestly not sure. My partner's interest is now piqued, and he has mentioned doing the Frances together, perhaps, but.... I dunno. Perhaps in a few years, once I've forgotten the pain in my feet.