We cannot calculate the payments for you here. However, the bottom will assist you in doing so.
"Calculating basic guideline support.
Note: in Pennsylvania, the person paying support is called the “obligor.” The person receiving support is the “obligee.”
1. Add both parents’ net monthly incomes to get a combined income total.
2. Divide the obligor’s net monthly income by the total from number 1, above. This will give you the obligor’s share of the combined income total.
3. Using the leftmost column of the guideline chart, find your combined income total, and then move to the right, to the column for the correct number of children. This is your combined basic child support obligation.
4. Multiply the combined basic child support obligation by the obligor’s share of the parents’ combined income from number 2, above, to get the obligor’s basic monthly child support obligation.
Example: Let’s assume that there are two children, that Father is the obligor and is earning $2,600 net per month, and that Mother is earning $2,200 net per month. Step 1: We add the two incomes to get a combined total income of $4,800. Step 2: We divide Father’s income of $2,600 by the total, and see that he is making about 0.54 (or 54%) of the combined total income. Step 3:According to the guideline chart, the combined basic child support obligation for two children with a combined total income of $4,800 is $1,325. Step 4:Multiplying that total figure by Father’s share of 0.54 yields his basic monthly child support obligation of $716."
As to your fourth question, she cannot simply quit her job or under-employ herself to try to collect more from you. That being said, if she unintentionally loses her job or suffers a decrease in income, then that would be taken into consideration in calculating the child support obligation and you would end up paying more.