ok i'll try and clarify some things to the best of my knowledge, so if I make any mistakes, hey fuck it, we're all human and here to learn a lil something:
a) Yes the claims are that Mohammad (pbuh) was illiterate. He Did not read nor write the Quran. There was revalations brought to him through the Angel Gabriel. Quranic verses were written down by his follwers, and compiled later on into the book itself. Most early Muslims knew the Quran through methods of memorization, from the revalations brought down to the prophet then passed on to his followers.
proofs of him being illiterate, I dont have, that was just something that from what I've read was just common knowledge among the people that knew him, therefore it made him more believeable. I know theres verses in the Quran and stuff that indicate that he was illiterate, but providing u guys proofs from there would kinda be pointless?
Now, according to Islam there is also proofs that he became literate as he gained prophecy. In the first revalation, Gabriel asked him to read, and he replied I cannot, and repeated his request, and the Prophet was able to do it.
b) Yes there as proofs that the Prophet married Aisha at a very young age. Now this is one thing i never really understood. But what I do know is that the Prophet had visions of marrying her in his dreams on 2 occassions, then asked her father for her hand in marriage. I've also heard that this was an accepted custom in Arabia at the time. But umm, I found a really long article on that which is from a somewhat credible source of Islamic knowledge, although it is a very (salafi/wahabi) website, so I dont agree with everything they say, but its the most comprehensive article i found so:
http://www.islaam.ca/what-is-islam-/women-in-islam/the-young-marriage-of-aa-ishah-the-wife-of-prophet-muh-2.html
Another thing I just wanted to sy is Islam doesnt allow the marriage of 2 ppl that dont completely agree to it. Although alot of Muslims have strayed from that and act like the man can just pick a girl and just marry her without a consent, this is far from the truth. So why the contradiction between the Prophet's action and the messege of islam? 2 reasons
a) There's is a Hadith where the Prophet said, 'If my actions ever contradict my statements (quran and hadith). Always refer to the statements. Because I'm only a man and make mistakes also, and I also fall victim to circumstances' (paraphrased)
b) There was certain things that the Prophet had done, due to revalations from God, that he did as a part of fulfilling prophecy, that didnt mean anyone could do it... which i dont believe is the case in this situation, since he would explicitly mention it after.
.. so marrying a girl at the age of 9, IMO is basically marrying her without her consent, since she's too young to make a decision like that, but now that becomes very subjective from society to society. Whats the age one can make that decision? 16? 18? 21?.. who knows.
I think when u study religion, what u believe and what u dont is just faith. Because most of it is just alot of history. So you cant really Prove anything that a man said or did in that era. You got written history books, but who decides whether thats PROOF or not and how accurate they really are? I dont know, to me, I believe in Islam, because I have an element of faith. I'm not a blind follower, I've juggled with many idea's and understand where an athiest is coming from. But uhh, if u study the sciences of Hadith it is actually a quite comprehensive method of evaluating it. But the problem comes when people interpret it.
And when it comes down to it, I cant prove to anyone that god exists. And no-one can prove to me that he does'nt. I guess its just something inside you. I feel at peace with my religion, but it makes me sad that its misrepresented by either uneducated modernist that are trying to make everyone else look bad OR uneducated extremeist that make everyone else look bad.
Islam doesnt tell u to strap urself to a bomb and kill innocent ppl, nor does it tell u to turn the other cheek. It doesnt tell you to force women to wear a nikaab nor does it tell u to let women OR men run around naked.
.. Sorry if I've made any mistakes, I was just shedding light on the situation to the best of my knowledge, and I aint trying to front like i have all the answers.
~peace