Hi,
@skotzko. I have done the Salvador, as has LTfit, and undoubtedly many others, in 4 days. They are long days, but I have done this in my 60s and 70s and you look like quite the youngster. And you have been walking for weeks now, so it seems pretty do-able for you.
The key is walking on the first day to Pola de Gordón. That’s a long 38 km, but with a good stop in La Robla, and a reservation in Pola de Gordón, you could saunter your way there. (I like Pensión 15 day mayo, but the rooms over the Mesón de Miguel are fine, too). From there, the next obvious stages are Pajares and Pola de Lena (don’t get your “Polas” mixed up). None of those stages is a walk in the park.
If you say you need to be in Oviedo on Friday, maybe you could also add Friday morning to your walking time. Mieres to Oviedo is a very do-able 19 km. There are three ascents, but they progress from stiffest to easiest so that’s nice.
With regards to your “which part should I skip” question, I’m pretty sure everyone would say Mieres to Oviedo is the one to consider. And it would be very easy, because Mieres is essentially an Oviedo suburb and has a lot of public transport options. And the nice thing is that it’s at the end of the walk, so you can have it as insurance in case you need to cut the walking short. But I don’t think you will. Buen camino and good luck with this!