I read a highly criticised Swedish translation so I think it's a bad source to quote anything from.
And then we have the benefit of knowing pretty much everything about Mohammed's life. It's even possible to check out his complete wardrobe in Topkapi palace in Istanbul. They even have letters that he's written, and foot, handprints and even shavings off his beard. I've been there myself and checked them out. It's amazing.
We know how he lived and what opinions he had. We know that plenty of the decisions where purely political. The move with turning around and facing Mecka instead of Jerusalem when they prayed was purely political. The three Jewish tribes in the area chose to align with Mecka instead of the Muslims. It was about showing them how seriously he took it. And once Mecka was conquered, there was no compelling reason to tell everybody to face Jerusalem again.
We also know that Mohammed saw Judaism, Islam and Christianity as the same religion with the same values, only catering to different cultures. So if Christianity doesn't have passages about killing infidels then chances are that "kill" means something different in ancient Arabic.
Another amusing thing Karen Armstrong points out is the distorted view of the crusades.
The Arabs at the turn of the last millennia paid very little attention to what was happening in western and northern Europe. When the crusaders took Jerusalem in 1099 the Arab/Muslim reaction was nothing. It's hardly mentioned anywhere in their texts from the time. Much less was seen as a problem. Jerusalem sat at the time just north of the large Fatamid muslim empire. They ignored it completely even though they where probably richer than all of western Europe put together and could easily have crushed the crusader states like a bug.
When Saladin retook Jerusalem in 1170 it was only because it was on the way to Syria. Politically he had used the crusader states as a buffer between him and the rest of the muslim world but now when he wanted to expand his empire they had outlived their usefulness. Saladin was just one lone Emir. He wasn't commanding any united Muslim army.
The focus and importance of the crusades as a deeply wounding attack on Islam is purely a 20'th century construct. It has no historical support or basis.
The western world as a economic and political superpower is a relatively new thing. The Arabs in 1099 saw the Christian crusaders as the little guy trying to at best annoy the giant. But they wheren't even very good at that.