Help with Sapin and Portugal itinerary please
 

I'm planning a trip in late May/early June to Spain and Portugal. I have 4 weeks leave time. The Camino de Santiago walk has been on my bucket list for a few years now and I've decided to walk the last 100kms this year.
So my plan so far is:-
Fly Adelaide to Barcelona (Friday)
Arrive Barcelona (Saturday)
Spend 4-5 days in Barcelona
Go to San Sebastian (2 days?)
Start walking tour from Sarria to Santiago des Compostela (7 days - Saturday to Saturday)
Travel to Lisbon and/or Porto (Saturday - 4-6 days?)
Travel to Madrid (4-5 days)
Fly back to Adelaide from Madrid
Have at least the weekend at home before starting work on Monday

But I am really struggling with logistics and can't make up my mind.....

How many days should I allow for Barcelona, Madrid and Lisbon/Porto?
How can I get from San Sebastian to Santiago des Compostela without breaking the bank or spending 10-12hours on a train/bus?
Should I not go to San Sebastian? Please suggest alternative small charming city/town.
Where should I go in Portugal? I have never been and thought Lisbon and Porto made the most sense. But open to suggestions.

I can also change the order of where I fly into. I can fly into Madrid and out of Barcelona.

As you can see I'm am very confused. Please help.....

Sorry about the typo in subject. I meant - Help with Spain and Portugal itinerary please.

Suggest you stay with your two days in Donostia/San Sebastian, something quite special, beautiful landscapes, a distinct culture that people take great pride in, some of the finest city beaches on the continent and the food capital of Spain. http://www.euskoguide.com/places-bas...stian-tourism/

To start your walk from Sarria to Santiago de Compostela, you better go by train from San Sebastian to Sarria with a stop in Monforte de Lemos, total travel time 9h 30 mins. Go after breakfast and be in Sarria in good time before dinner.

Thanks Kinhe. The more look into the San Sebastián, the more I know I need to go. But almost 10 hours on the train?
Has anyone here done a long train journey in Spain? What was it like?

The trains in Spain are generally very comfortable: http://www.seat61.com/Spain-trains.htm#.VsDgy4f2aM8

Most of this trip will be on an intercity/Alvia train with bar/cafeteria etc. http://www.renfe.com/EN/viajeros/nuestros_trenes/