It was not too long (though I only came to that opinion after reading it) and I have no idea how you do it, but with that huge character list, it's still amazingly easy to remember who is who, who did what and what is going on.
Glad to hear that. I try, but to tell the truth sometimes I have a hard time remembering all of them myself.
[About often seing ASOIAF English-language books in Lisbon]
Very interesting. I had no idea. I assume these are English copies? So far as I know, I am not published in Portugese. In Spanish, yes, but not Portugese.
Speaking of which, I am about to leave for three weeks in Spain. I am a guest at a festival called Semana Negra, held in Gijon in early July. Unfortunately, I will not be able to visit Portugal this trip, as much as I would love to. But if there are fans there who would like to meet me, they should come up to Semana Negra.
Does Sam still have the horn that Jon found with the obsidian?
Yes.
And is the lord of Horn Hill really Sam's father? (I like Sam very much, BTW)
Well, so far as anyone knows. Why wouldn't he be?
Is Barristan, for his personality and for being a member of the Kingsguard and keeping the king's secrets, a good witness about Varys influence over Aerys?
A witness, certainly. A good witness? Well, there were things he was not privy to, and of course he saw events from his own standpoint.
About some characters being named Lymond and other possible references to Dunnett's books
The books are full of homages, but not, alas, to Dunnett. Sorry. I have read only a little of her work, though I have heard so many good things about her that I do want to read more.