1.Did the Prophet Muhammed (saw) kill 400,600 or 900 Jews as stated in the Seerah of Ibn Ishaq (I know that Imam Malik denounces Ibn Ishaq outright as "a liar"and "an impostor").
2. Ibn Ishaaq states that Muhammad took one (Jewish) woman for himself:
"The apostle had chosen one of their women for himself, Rayhana bint Amr . . . one of the women of Banu Qurayzah, and she remained with him until she died, in his power. The apostle had proposed to marry and put a veil on her, but she said: "Nay, leave me in your power, for that will be easier for me and for you." So he left her. She had shown repugnance towards Islam when she was captured and clung to Judaism." (Ibn Ishaq p. 466)
3. Are the next Hadith Sahih and what is the meaning of this Hadith: Book 14, Number 2665:
Narrated Aisha, Ummul Mu'minin: No woman of Banu Qurayzah was killed except one. She was with me, talking and laughing on her back and belly (extremely), while the Apostle of Allah (peace_be_upon_him) was killing her people with the swords. Suddenly a man called her name: Where is so-and-so? She said: I I asked: What is the matter with you? She said: I did a new act. She said: The man took her and beheaded her. She said: I will not forget that she was laughing extremely although she knew that she would be killed. Jihad (Kitab Al-Jihad) Sunan Abu Dawud
4. Narrated Abdullah ibn Amr ibn al-'As:
The Apostle of Allah (peace_be_upon_him) was asked about the aqiqah. He replied: Allah does not like the breaking of ties (uquq), as though he disliked the name. And he said: If anyone has a child born to him and wishes to offer a sacrifice on its behalf, he may offer two resembling sheep for a boy and one for a girl. Why 2 for a boy and 1 for a girl? What is the meaning of this?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The scholars differed in opinion about the number of the Jews who died in the battle of Banu Quraythah. The least number that was reported in this regard is that they were 400; this is proven by an authentic narration reported by At-Tirmithi and An-Nasaa'i . The highest number that was reported is 900, and this is reported as you mentioned by Ibn Is-Haaq .

You should know that the Jews of Banu Quraythah deserved this as they betrayed the covenant. For more benefit, please refer to Fatwa 99502.

The scholars also differed in opinion about the issue of Rayhaanah. Some of them stated that she embraced Islam and the Prophet married her after he freed her because she was a slave girl. However, some other scholars stated that she remained as a slave of the Prophet . For more benefit, please refer to Fatwa 90599.

As regards the narration on the woman from the Jews of Banu Quraythah who was killed, it is a Saheeh narration. The interpreters of this narration stated that the reason she was killed is that she insulted the Prophet . This is the evidence given by many scholars that whoever insults the Prophet should be killed.

You should know that Muhammad ibn Is-Haaq is a great scholar, and he is the author of the book entitled Al-Maghaazi (The Conquests), which is a reference book in biography and history.

As for what Imaam Maalik said about Ibn Is-Haaq, then this statement should not be considered as stated by the scholars because these two scholars lived at the same time and they might have had some arguments between them.

In addition to this, what Ibn Is-Haaq stated and which you mentioned in the question was also reported by other scholars .

With regard to the wisdom of the 'Aqeeqah being two sheep for a male born baby and one sheep for a female born baby, then the scholars stated that this wisdom could show the virtue of the male over the female. This is the legislation of Allaah; He should not be questioned about what He does.

Finally, it should be noted that it is acceptable to slaughter only one sheep for the 'Aqeeqah of a male infant as the Prophet slaughtered one sheep for the 'Aqeeqah of Al-Hasan and one sheep for Al-Husayn .

Allaah Knows best.