Been doing some experimentation with trying to maintain 4-5 traits consistently and it feels remarkably rare for an offspring to carry on all traits even if both parents have the same traits. Additionally, while the MC does not have listed stats, it appears that they are in fact incredibly low. If you breed a 100 stat across the board female with the MC, the stats will always be lower. It would be great if there was a way in the future to raise the MC's stats to deal with this, or to allow more consistent trait inheritance.
The inheritance mechanics are known:
For stats, stat
modifiers are being heritable. The child gets a random number between the lowest of the parent values, and highest of parent values, with a small chance of a mutation that makes them even better than the parents.
Currently, MC seems to have stat modifiers of 0, which is why it's hard for him to have a child that is as good as the mother. I agree that introducing a mechanic to improve MC's stats is a good solution. Perhaps succubus magic can help with that.
For traits, the number of traits that are inherited is random, with higher numbers being more difficult. It doesn't seem to matter how many of the parents have the trait.