The central route typically takes about 10 days walking. Add two days / nights for Santiago (minimum). That fits within your timetable.
Also, having grown up in New Jersey and now living in Florida, seeing the same Atlantic Ocean from the other side is not very exciting or enticing for me. I have tried the coastal route up to Villa do Conde, before cutting in toward Rates and the Central Route. On my second go from Porto, I rode the local train / Metro to
before Vilarinhos and walked from there. I stayed at a very nice private albergue called Casa Laura. See below...
This is also about two days walking before Casa Fernanda. As regards staying at Casa Fernanda, please, please reserve a place early. She is very popular, and with good reason. So, her beds fill up fast. While she operates, or did, as a donativo, DO be as generous as you can.
Consider spending one night in Porto to rest up and prepare before heading north to Santiago. You may need / want to post things ahead to Ivar at Santiago to await your arrival. The Portuguese post office is called CTT. Here is their website:
https://www.ctt.pt/home/index.html
To have time to mail stuff ahead, you will need that extra time. Also, in my experience, you will be exhausted from being cramped in the airplane for 9+ hours. Don't push it.
Plus, Porto is a beautiful, historic city and well worthy of spending time there. If pressed for time, consider the hop on-hop off tourist bus for a good view and tour of the important places in the city.
Also, Porto, like most other large cities has an industrial belt of light industry, warehouses, trucking distribution centers and big box stores surrounding it. This is true of Lisbon, Madrid, Leon, Burgos, and even Santiago to a lesser extent.
You can choose to walk across this distance, OR opt to ride public transportation to effectively leap-frog, saving most of a day's walking. This is 'legal' as only walking the final 100 km before Santiago is what qualifies you for a Compostela. Anything beyond that is for your benefit and pleasure.
Here is the Metro Porto website:
https://en.metrodoporto.pt
Also, here is the Portuguese Railways website:
https://www.cp.pt/passageiros/en
I cannot recall if I actually rode the Metro or CP train, and then walked, but I know I did take one for perhaps a 30-minute ride, before getting off to walk. The scenery enroute convinced me that I made the right decision for me. Having grown up in northern New Jersey, seeing industry does not exactly make my spirit soar, and it is no way IMHO to start a Camino.
In this case, I chose to ride the train / metro out past the urban belt, and then walk to Vilarhino. There I stayed at Casa Laura. Here is their Facebook page:
Casa da Laura, Vila do Conde. 1,317 likes · 84 talking about this · 1,152 were here. Albergue para Caminho Santiago do Porto (Vilarinho - 1ª etapa) Reservas/Reservation: 917767307
www.facebook.com
I highly recommend this private albergue.
Lastly, even in the off-season, DO NOT arrive in Santiago without a reservation. Forewarned is forearmed... I recommend two nights. The night of arrival and the next, to provide enough time to handle business at the Pilgrim Office and see Santiago. You will not be sorry you did this.
Hope this helps.