If you gave part ownership to your wife in 2017, then that would be a "deemed disposition" for you. You should amend your 2017 return to reflect that disposition. For 2019, since both you and your wife have ownership of the home, both of you would fill out the principle residence worksheet on your respective returns.
The Adjusted Cost Base is usually the cost of a property plus any expenses to acquire it, such as commissions and legal fees. It can also include capital expenditures, such as the cost of additions and improvements to the property. For a deemed disposition, the ACB would be the fair market value of the property at the time of acquisition.
