Where would one go to edit the fertility values of the girls?
You can use "fertupgrade" in the console. It doesn't change the fertility of the girls, it changes YOUR fertility. It's the variable used by the fertility upgrade you buy in the store (5 for the first upgrade, 10 for the second). So, set that to 99 or something and it will give you max-fertility and a (nearly) 100% impregnation rate. (If the girl doesn't get pregnant like this, then there's a specific reason. See below.)
The reason to do it this way instead of changing the girls, is because there are many, many events where the girls are not meant to get pregnant. It's part of the story line that they don't get pregnant, and the story line sets their fertility to 0 temporarily to make sure of that. If you got them pregnant, it would break the event chain. So by keeping them infertile when necessary by only changing YOUR fertility, it circumvents that.
Final note, the event chain for the Oracle might (but probably won't) change this. Buying Fertility upgrades from the store will
definitely change this and you'll have to reset it to 99 or whatever afterwards.