You need to verify, based on common law 20-factor tests, whether the taxpayer is really an independent contractor.  If he is indeed an independent contractor, the income should be reporting on Sch C instead of on Line 7.

Looks like he is getting his immigration status adjusted based on his marriage to the US citizen.  Does he actually have the proper immigration status and authorization to work in the US?  Not directly related to tax and should not be a consideration for tax compliance but it's something you should caution him to consult with his immigration attorney.

As mentioned in my comment, there may be more than meet the eyes.  By his presence in the US and relationship with the foreign entity, he may already have created PE exposure to the foreign entity (especially if he is a common law employee or an agent who represents only that entity), not to mention potential lapses in the various reporting/withholding compliance requirements.