If it was just sarcasm (I couldn't tell ; )), then my apologies.

Well, thanks everybody, your inputs are being very valuable to me.

Each one of your advices I'll follow, but I still think our bikes need more speeds, expecially if loaded and when climbing.
I'm having an hard time to find someone that could "operate" our Dahons to add more speeds. It looks like that in Spain we lack both spare parts and workforce when it comes to folding bikes, expecially Dahons.

I'd love to have a real bike made for me by Bike Friday but what will happen if for any reason I don't like it or it simply needs adjusting? Buying a bike online scares me, even more if it comes from another continent.
I may be able to find an Airnimal Joey Explore though. How is it?

Anyway... it seems that Tern is much more present than any other brand here, so in perspective I think it's better to sell our bikes and purchase two Terns with more speeds and than build up from there, at least we could find better support in the future.

You might visit the XOOTR swift website and consider one of their folders. Base bike is at 799 and has 8 speeds but is extremely customizable. A front derailleur is available. You can read about them here in bike forums adn they are supposed to be great riding and very sturdy. Just a thought.

When I went for more speeds I bought a dual drive hub. There are also dahon apadters available for a front drailler.

We were carrying 27kg between the 2 of us, excluding food and water. Early on I started carrying all the heavier stuff in an effort to equalise our climbing speeds, as I am very fit while she is just an occasional rider. (that made no difference.) She was left with about 7kg and me with 20kg. My bike and rack was sturdier so coped better with the extra weight. Our average speed in the saddle including climbs and stuff was 15km/h. When factoring in rest stops, we average 10km/h, so it's easy to calculate our arrival time and necessary departure times.