Just seen this, but my suggestion is to aim for San Juan de Villapenda at the end of the 1st day, Bodenaya the 2nd then Borres for the 3rd, if anybody else is walking those are the most likely places they will go for and that will be open. Once you are into Galicia they have the Xunta Albergues and they usually have a commitment to opening 365( or 366 next year) days a year. You will have options of bailing out at various points, which isn't a sin, sometimes its commonsense winning out over determination. I have just had a similar pre-camino decision to make on another route which I was due to start on the 14th December, it has only 1 Albergue along the route the other places I could stay such as hotels were not taking bookings for the days I wanted to be there, when I added that to probably lots of rain,my own personal fitness, lack of daylight hours, remote mountain sections I decided to look at other routes.
The Primitivo is definitely doable but you have to know when to take a step back, the really remote and tricky sections will be from Borres to Cadavo, I watched a video of pilgrims walk the hospitales route in snow but decided at Fonsgrada to bus to Lugo because the next section while not having the same reputation as the hospitales was just as tricky and remote.
Buen Camino