When there is a spousal and/or child support order, an Income Withholding Order is a matter of right. No, you cannot stop it. Perhaps you can have it temporarily set-aside while you get yourself approved for the loan and then have the order reinstated after you close escrow. Discuss this option with an attorney.
A wage assignment (not wage garnishment) should be used to deny you a mortgage. I suggest that you appeal to the mortgage company for this. You shoudl also see an attorney on this matter.
You will need an attorneys assistance.
My name is Stephen R. Cohen and I have practiced over 38 years and can be reached at 213-819-1171. I practiced mainly in Los Angeles and Orange County, California. I am not seeking clients from existing relationships with other attorneys, and give only limited advise over the phone (the phone is primarily used to set appointments), these services do not create an attorney client relationship. I apologize for mispelling< as I am a lousy typist, My answers may offend as I do not believe in pulling punches or sugar coating the truth. Further regarding courts in other states my opinions are largely based on logic and what I think is the modern trend which is to consider the needs of the child.