Keep it clean and uncomplicated. Each does their own I-864 without listing the other's income.
Mom's household--Mom, sister, immigrant (your wife is married now and not a dependent is my general opinion)
Wife household-- wife, immigrant (Mom is not her dependent)
It doesn't matter really what the previous tax returns of your wife say because you are required to list the information from them, so no getting around it. If wife now has a full time job, then tell her CURRENT income in Part 6 #5. Current monthly salary times 12, for example. Then because her tax return doesn't show it, prove it in another way---a letter from her employer saying she works full time and makes $xxx.xx. Or pay stubs for about 6 months showing current income.
The DS-3025 can replace the I-693 immunization form (you said I-485) if every needed shot is listed, and it is filled out correctly.
