Lava cools leaving imprints of the instantaneous magnetic field of the earth over geological time. The interaction of the magnetic field drift and reversal, the precession of the earth, the axial tilt of the earth, and the plate movement of the earth is not well understood. It is basically governed by chaotic system interactions. For example plate movement can cause earthquakes which are as of yet unpredictable.
Again what the precession and tilt were like for the "pre-earth" is mostly a mystery.
Could a meteor impact like that which killed the dinosaurs 66 million years ago have altered or created the wobble?
The impact that created the moon was with a Mars sized body and definitely effect the earth's precession and tilt.
Are there any factors dampening or increasing the seasonal wobble over time?
Moon damps the tilt over geologic time. The instantaneous flow of the liquid magma inside the earth may increase or decrease the precession and/or tilt, but as the earth cools the overall effect is to decrease both.
Could a meteor impact like that which killed the dinosaurs 66 million years ago have altered or created the wobble?
There are theories that linked the extinction of dinosaurs or meteor impact million years ago such as India-Eurasia Collision which created the modern Himalayan which causes flattening the pole and elongating the surface that changes orientation on axial tilting. Meteor impact theory might not be enough to killed the dinosaurs 66 million years ago. Climate should be seen as a major factor that makes extinction for a certain species. Yet smaller biodiversity are more likely to be adaptive to harsh climate condition enable them to survive and evolve later years.
Are there any factors dampening or increasing the seasonal wobble over time?
Wobble might increase or decrease over time when plate tectonics shifts postion. This is because the distribution of plates varies to the degree of rotation of the Earth. Such as in our generation 2000 AD, looking on geodetic Earth and bathymetric structure leads you to observe flattening of the pole and elongation at equator. The contribution of Himalayan mountain and subduction of the Pacific trench affects the speed rotation thus altering different cycles calculated such as precession and obliquity of the true pole.