1. In allowing his daughter to be placed with the mother, how long does the daughter have to live with my fiancée before she can file a motion for full placement, claiming there has been a substantial change in circumstance since the last order substantially affecting physical placement?
There is no set time; most probably wait an average of 6 months. Mainly, because he could say she was just on an extended visit. After 6 months, it would be clear it is permanent.
2. In giving up placement of the daughter so soon after winning in court, would the court view his motion for modification as a tactical maneuver in order to get out of paying, or paying as much child support?
No.
3. She has 90 days to file an appeal on the decision, should she file an appeal, and then file a motion for placement of her daughter, then after filing a motion, request leave from the appeal until the motion has been heard and decided on by the court.
There's nothing to appeal. The court did what it thought best, and is within the scope of the law.
4. If the court determines that the motion was filed as a tactical maneuver by the father, and not from his being concerned for there wellbeing, then, can she ask that her attorney fees from her motion and attorney fees from the post divorce placement dispute, (his motion), be paid by her ex-husband?
You would probably only be successful if the ex-husband, in writing and notarized admitted to doing so.
5. When filing a motion for full placement of the daughter, should she also include full placement of her son if her son has close ties with the daughter, and he misses her, would the court consider keeping the two together?