1. Yes, this is the correct place for the retirement contributions that you made for the benefit of your employees (you wife in this case). You can include wife's elective deferrals on line 19 as long as you do not also include them on line 26; in this case line 26 would only include the amount in box 1 of your wife's W-2.
2. The spouse's column would only be used if your spouse was also self-employed. Since your wife is your employee, not self-employed, her retirement contributions do not go in the spouse's column next to your contributions.
3. Checking the spouse's 401(k) Maximize box does nothing because your wife is not self-employed.
