Sorry to hear that you had to pay for a house you already owned, been there done that. These snakes sure can end up with many things that don't rightfully belong to them, yuk.
The income that he recieved from you for the splitting of the assets is not considered income that could be counted as income for Child support purposes. This was a settlement on property that was an amount owed to him, not as income but like a loan to someone that had to be repaid.
As for taxable income it is most likley not, unless it was a capital gain. Did he have value in the home of a certian amount and then the court increased that value by making you pay him, or did you basically pay him for half of the asset minus anything he owed to you? If it was straight splitting of the asset value than no it is not taxable.
As for more child support I hope you have figured out how toprove his income legally, the bank statements would be ideal.
If you have special cercumstances for your children such as expensive sports that they play in, you could ask the court to order he pay half in addition to court order child support, or maybe one of the kids play an instrument, the court could order he pay half of the instrument expense. I would look at anything in addition to the normal child raising expenses and see if you can come up with something....it could even be he be mandatory court order to start a 529 college fund if at the time you were married it was agreed the children would be going to college. This works great if one or both of you have an under graduate or advanced degree.