Dan you could file ammended returns to show your true income over the last years. That may cut into your 90k that you have saved because you would have to pay back taxes and maybe some interest. After you have come clean and payed what you owe to all of us (We the people) you may be able to qualify for a loan on a smaller house.
It would also be nice to be able to keep your house as the IRS is at some point going to see 90k in the bank and reported income at a level that can not justify the savings. Audit time for self employed! - Earlier today