
If Folic acid is given, 5 mg/day is a recomended dosage to a 35kg bitch. Don't think you need to reduce the dose for a smaller bitch, humans take the same, whether they are 50 kg or 150 kg :-D
In RRs as Ridgielover said, we give it to reduce the number of dermoid sinuses. For us it's during the first trimester (first 3 weeks of preganacy) it might make a difference, after 3 weeks it's too late anyway, as the spine is created by then. For cleft palates I don't know, but as long as it's given no later than from first day of mating, you can't go far wrong. It's not too late, anyway. I haven't heard any facts about it having any sideeffects, but maybe someone else who has, will come along.
Good luck,
Karen