If you entered the US in 2012 on an F-1 visa, you were exempt from the substantial presence test for 2012, 2013, 2014, 2015, 2016. Starting January 1, 2017 you need to count your US days of presence. So you are a resident. Your wife is also a US resident in 2019.
I cannot tell you whether the US China treaty applies but can direct you to Publication 901,
China, People's Republic of
An individual who is a resident of the People's Republic of China and who is temporarily in the United States primarily to teach, lecture, or conduct research at a university or other accredited educational institution or scientific research institution is exempt from U.S. income tax on income for the teaching, lecturing, or research for a total of not more than 3 years. This exemption does not apply to income from research carried on mainly for the private benefit of any person rather than in the public interest.
A student, business apprentice, or trainee who is a resident of the People's Republic of China on the date of arrival in the United States and who is present in the United States solely to obtain training, education, or special technical experience is exempt from U.S. income tax on the following amounts. Payments received from abroad for maintenance, education, study, research, or training. Grants or awards from a government, scientific, educational, or other taxexempt organization. Income from personal services performed in the United States of up to $5,000 for each tax year. An individual is entitled to this exemption only for the time reasonably necessary to complete the education or training.
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