Your proposed route is almost identical to mine.
I did San Seb to Zarautz, Zarautz to Deba, Deba to Markina and then exactly as you plan. And kt is a beautiful route.
But so is the Meseta. If You arw thinking of skipping it because you have read it is boring, I can assure younot is not. In fact that infamous 17km stretch with nothing in sight is oneof my most beautiful days on the Camino. Nothing but big blue sky! Just stop or skip when you feel it is right for you.
On tne Norte, aim to make lunch your main meal: menu del dia rocks! Then have a light snack in the evening, unless you are staying in an albergue that includes dinner.
Between Zumaia and Deba, if you chose the easiest route (and miss the flysch), there's a hamlet called Eloria, just after the park. There you will find a cafe that looks like nothing but that wasrun by a most wondeful and generous lady when I crawled in it after not having had much for breakfast, and willing to settle with a can of tuna: she brought be a beautifully grilled tuna steak! And ask for Txacoli, the bubbly wine made in the vinayard across the street.
Markina has a great albergue in a converted bid coop of some sort: Inxauspe. It's a 3 minute walk from the center of town, with lawn chairs to rest on in the front yard.
Don't forget to book ahead in Guernika as it fills up quickly. The juvenil is where I stayed and it was fine.
Bilbao: I made the mistake of staying in a perfectly located albergue open to anyone (not just Camino people) and Bilbao being a party town it was a disaster. I would recommend a pension, hotel, or a pilgrim only albegue.
Nice bakery in Portugalete by the metro station.
In Pobena, there's a restaurant to thr far right of the plaza that offers a very nice menu del dia.
Liendo! Excellent choice, rather than going all the way to Laredo. I stayed at the Santurino albergue and the hospi showed us a way out of town through the hills, not the road. It was gorgous! At the top of the hill is the Ermita de San Xulian ruins and a beautiful little beach.
Noya, also an excellent choice. I stayed in town at the Casona Azul, on the plaza. It was the tourism office who told me they have a pilgrim room: a room with 2 single beds and a full bathroom. A lovely family runs it.
But the way into Noya can be tricky. There's a steep hill, El Brusco. Steep. With nothing from orcent you from falling down the cliff if you fall backwards. You can also walk around it by road.
You will have a wonderful time!