So you don't believe that such a close pass to Mars, that Mar's gravitational tug on Ison couldn't alter the orbit of Ison?
Yes, it of course it would, but it's not going to. Such motions don't happen by surprise. The motions of ISON as it approaches Mars and continues on have already been calculated. Nothing in the vacuum of space can change that motion.
So you don't believe that "a chaotic zone of dust and debris" is what makes up a comet's tail, or is left behind in the orbit path of a comet?
Yes, comets shed debris in the form of specs of dust and sublimating ices. They don't however "swirl along" picking up objects and debris as they go. You are envisioning motions and interactions that happen in air or water. In the vacuum of space there is no "swirling", or "dragging along." The motion isn't even that chaotic since in the near-vacuum of the comet's tail, particle interaction is minimal.
Then explain the Leonids and why they affect us every year.
The Leonids (and every other meteor shower) are caused when the Earth crosses the orbits of the sand and dust-sized particles left by Comet Temple-Tuttle during previous passes through the inner solar system. There is a ring of material left floating in space around our sun. The Earth passes through these rings of material roughly the same time every year. When the particles encounter the Earth's atmosphere they burn up and give off a flash of light as they do so. That's the only "effect" they have. The particles were certainly not drawn in by Temple-Tuttle by way of "dragging" or "swirling" through the asteroid belt. Most importantly, none of this is ever a mystery or a surprise, the motions of comets are never unknown, nor do the motions "change" at the last moment.