*Sigh* Must everyone always argue? Alright children lets get this all strait :-p
1. Kahanism is for the most part is simply believing in what Rav Kahane zt''l said, which is simply believing in and following the words of the Torah. Yes Bnei Noach can be Kahanists, but I doubt they are nearly as die-hard about it as Jews are. But as I said its simply believing in the words of the Torah and being willing and ready to follow though with it. As Rav Kahane zt''l used to say "This is not Kahanism! THIS IS JUDAISM!"
2. Yes according to Judaism you must kill someone first before they kill you - though you must be 100% sure. But YOU MUST KILL YOUR ENEMY. And no that does not mean "oh I hate so and so so - I must kill him; it means if you see an Arab terrorist, it is your obligation to kill him before he kills others. This is both in the Tanach and the Gamara.
3. If you take a pig and call it a cow and say it is kosher does it make it so? Of course not! Just as when you take a pagan G-d and say it is HASHEM? NO IT IS NOT. As well if you are to take two pagan gods such as lets say.... Aphrodite and Hera and you worship one and someone else the other, though you are worshiping the deities exclusively and only believe that the one you worship is all powerful and the only G-d and creator making you monotheistic does this mean they are the same one since you are worshiping just one deity? Or does that mean they are not pagans just because you and another are worshiping them monotheistically? Of it doesn't. So just because Allah is a monotheistic deity does not make him HASHEM no matter how you want to put it, he is a pagan G-d and that is that.
4. I will agree that Islam is not idol worship when it comes to worshiping a statue, though it is a G-d. Though according to many the Kaaba was used for such worship. According to some it was dedicated to Hubal, a Nabatean deity of the moon, and contained 360 idols which probably represented the days of the year. According to others, the Kaaba was a shrine for the daughters of G-d Hubal; al-Lat, al-Uzza, and Manat, and then again according to another about four hundred years before the birth of Muhammad, a man named Amr bin Lahyo bin Harath bin Amr ul-Qais bin Thalaba bin Azd bin Khalan bin Babalyun bin Saba, who was descended from Qahtan and king of Hijaz, had placed a Hubal idol onto the roof of the Kaaba, and this idol was one of the chief deities of the ruling Quraysh tribe.
I can go on and on, but point being if it was erected to be for idols, or if it even still has one in it then it would be idol worship since they are praying towards the Kaaba even if they are not praying to it itself but rather praying towards it the way we do to or towards the Kotel.
5. The only reason they say they are praying to HASHEM is because they are the children of Ishmael who was one of the sons of Avraham so it was easy for Mohammed to just say it was HASHEM the G-d of their grandfather. Mohammed also had been trying to entrap the Jews, so chances are that is where he even got the idea at first to say it was HASHEM. He even used to have everyone pray towards the Kotel like we do, to get Jews to convert - which thank heavens didn't work even though it did lead to him loathing the Jews as well as everyone else who did not convert. But since many pagans were converting to Judaism because polytheism/paganism seemed illogical, leaving them feeling like something was missing and they wanted something more possible like monotheism in which case it became easier to convert pagans to Islam since you already have what they like and were used to such as murder, rape, theft - and frankly its is much easier then Judaism to follow, other then praying two times a day more then our 3. And since it is such a strong religion - though it did not start out AS strong as it is today - it made them feel they might actually have found something worth worshiping even if it still was paganism which they probably didn't even realize it was. And further more Mohammed was trying to get Pagans to convert also, so what is a better way to do that then to take one of their deities say it is the only G-d, say this is a monotheistic religion and that's that. He even kept the simple of the deity, or did you never wonder where the idea of the crescent came from. So again, Islam may not be idol worship but IT IS paganism since it is not HASHEM they are praying to.
6. The death penalty for believing in polytheism is as has been already said; only for people with in Israel and NOT all over the rest of the world. The however only thing that does happen to all pagans all over is they brake one of the 7 laws bnai noach.
P.S. To all those who take things extremely seriously and were offended by my saying "*Sigh* Must everyone always argue? Alright children lets get this all strait :-p" and felt I was speaking condescendingly to them, I am sorry I was only joking and didn't mean to offend you.