Certainly consenting to zero children can seem a bit weird, but there are basically two systems: getting consent and persuading them to adjust their preference. The simplest solution would be to remove the zero option.
I'm not seeing any obvious code for the starting slave, so it's not clear why they would be affected. The base game has some lag issues, mostly from image updates, that get out of hand with Aric's mod. Some solutions have been implemented, but are only in the GitHub so far.
Image selection by sex is mostly outside the scope of this mod. The proper fix would involve changes to the Improved Random Portraits mod. Though it should be possible to temporarily change the person's sex if no image is assigned and then try again to find an image.