Can it be somehow estimated, how reliable degeneration is in its effects? How much worse will every level of degeneration be, in probability of detrimental genes appearing, or in percentage of the genetic makeup worsening?

The main reason for my question is the fact that, while I have bred level 1 degenerates with two detrimental dominant genes, I have also managed to breed a level 2 degenerate with two beneficial dominant genes, majority of recessive genes being beneficial and only a single one detrimental, which is moreless on par with many ordinary animals with no degeneration. 

The chance of bad genes being introduced in a degenerated pet is 10% per gene per level of degeneration. So a DG3 would have a 30% chance per gene, on top of the gene power for all negative genes increasing. This is confirmed by Angel here.

If my math is correct, the chance of breeding a DG1 with no negative genes (from two adults with no negative genes) is 43%, the chance for a DG2 is 17%, and the chance for a DG3 is 6%. But this doesn't necessarily reflect the chance of producing a bad pet, because a negative gene might turn out to be recessive.