It is my layman's understanding that the impactor that created the moon probably had far more effect on the Earth's tilt, rotational velocity, and orbital eccentricity than anything else that came after it. That impactor was theorized to be the size of Mars, which dwarves the impactor at Chicxulub*. ALL impacts impart some energy to the planet, so your hypothesis has merit, but many of the microscopic changes to our planet's magnetic, rotational, and orbital characteristics cancel out over time because impacts happen in varying directions, Earthquakes happen on all sides of the crust, and 2-yr olds jump up and down on their beds constantly (mine jumps very high).
The Earth's wobble would probably be extremely high regardless of its history, if other planets are any indication. The Moon, which I have hinted probably had the biggest effect on it (that we know of), has actually been responsible for slowing the Earth's rotational speed down along with stabilizing its tilt (among other things). So again, while the*Chicxulub impact probably resulted in a tiny change to the characteristics you mention, you don't need to factor it in compared to the largest impacts our planet has seen (during the initial formation of our planet in its accretion phase,*Chicxulub-sized impactors could have struck DAILY).
Regarding the Earth's magnetic field, this is generated from the magnetic dynamo at the Earth's core. Again, there is almost no chance it was affected by the*Chicxulub impact. However, just for argument, the impactor probably DID deposit SOME iron onto the surface, and possibly even beneath the outer crust when it blew a hole in it, so maybe a tiny fraction of that iron did find its way to the core through convection or other transfer mechanism. Of course, if such an impact happened while our planet was still molten, then it is quite possible that a majority of the iron could have reached the core and added to the magnetic dynamo. The amount is still statistically insignificant, but worth noting. And perhaps the shock waves from the impact caused the inner mantle to oscillate over the core in a way which disrupted the magnetic field for a short time. But once again, I see little lasting impact.
Lastly, I have seen the theory regarding the Earth's orbital oscillation through the galactic plane, and the concept that our planet is more susceptible to cosmic rays when out of the protection of the galactic disc as well as more likely to pass through interstellar debris during these travels, and the possible link to extinction events. The theory is intriguing. I most recently read it while reading "Death From The Skies", by Phil Plait. Fun reading, but it is not a grand thesis on the matter either. I'll consider any theory, though. :)
Hopefully I didn't mis-state too many things here, and helped out a little. I'm not an astronomer or physicist, but I try hard!
