(petitioner and father-in-law purchased principal residence for petitioner and spouse; spouse lived in home with petitioner, but was not included on title and did not sign note or mortgage on residence - mortgage was $1.35 million; petitioner files as MFS and deducted the interest on the full $1.1 million allowed by I.R.C. Sec. 168(h) (entire debt, including interest, paid off in 2007) ; court holds that petitioner's deduction limited to interest paid on $500,000 of home acquisition indebtedness and $50,000 of home equity indebtedness; 20 percent accuracy-related penalty imposed).