Well, I couldn't really get in any info about Dorne except to say that we will see more about in A Feast For Crows. But I was able to ask some other questions and did get some info.
Question 1: It is noted on occasion that members of the Kingsguard have led armies. Specifically, Prince Lewyn, Jon Darry, and Barristan Selmy in the War of the Usurper and Selmy again in the Balon Greyjoy rebellion. Is this a normal happening or a rarity?
Answer: It has happened quite a bit throughout history. The fact is, Kings are more likely to trust the Kingsguard and their loyalty than the High Lords who will be looking out for themselves.
Question 2: What made Balon Greyjoy believe that he could successfully rebel against Robert considering his limited strength.
Answer: Balon Greyjoy did not believe that many of the Lords would answer Robert's calling of the banners because he was still viewed as an Usurper.
Question 3: It had been stated that Howland Reed would come out in The Winds of Winter, which is the 5th book. Will he still come in the 5th book (A Dance with Dragon)?
Answer: He will appear eventually.