As an employee, you are responsible for the employee share of the social security and medicare wages.
You will need to file Form 8919 to report the uncollected Social Security and Medicare tax on your wages.
I would only enter income on 8b (A) and not on 1 as your wages do not come from Form W2.
You do not report the Chinese taxes on the Substitute W2 Form 4852. You will claim them on Form 1116 as General category income taxes paid.
TurboTax does not contact the IRS on your behalf with Form 4852 - the form will go with your tax return.
Your return may need to be printed and mailed with this form.
You employer's arrangement is irregular - employers doing business in the US, even foreign employers are required to register and get Employer Identification Tax ID Numbers if they have employees in this country and comply with employment tax laws.
You are not subject to withholding tax to a foreign country on income earned in the United States.
The IRS could deny your Foreign Tax Credit as the tax is not legally owed to China.
