Thank you. You are entitled to take FMLA for your wife's serious health condition if you are required to care for her, so I don't understand why you would not have applied for that or why your employer didn't raise the issue. You can read about FMLA rights by going to: http://www.dol.gov/whd/regs/compliance/1421.htm
The reason I keep coming back to that is that absences associated with FMLA are the only ones that the law provides job protection for. In other words, an employer is free to use absences that are not related to FMLA and work production changes (if any) against an employee for attendance or discipline purposes as long as they would do the same for other employees who were away from work for any other reason other than FMLA.
Of course, an employer cannot treat someone more adversely simply because they are associated with someone who is ill or has a disability (temp or perm), but again, they can enforce production and attendance issues. The ADA
reasonable accommodation rules do not apply to employees who want accommodations to take care of a sick family member. The reasonable accommodations rules only apply to the employee's own illness. So, that would not afford you any job protection when you take time off or ask to work from home.
Your best course of action is to right now request intermittent FMLA for the care of your wife when needed. Her doctor will have to certify that she needs the assistance, but if they do, you will then have protection against your time away from the workplace counting against you.
Please feel free to ask follow up questions if you have them. I would be glad to assist you further if I can.