Current Income for your household
Yes - This is independant of the I-864. That's why the answers are in ranges as they want an overall picture of your finances as part of the determination of Public Charge Inadmissability.
Yes - You should include it as part of the liabilities in determining the range of your liabilities
This would be professional Certifications - Again this is part of determining the Public Charge Inadmissibility question. When they do this, they take an overall picture of your fianances, education and any professional certifications so they can make a judgement call on your prospects of being able to find gainful employment, not get sunk by a ridiculous amount of debt, your age, health, if you are prone to institutionalization at public expense, etc.