If you are filing a Sch C as a disreguarded entity then you should not also be filing an 1120 for a corporation.
A nonresident alien cannot use TurboTax. A nonresident alien has to file Form 1040-NR, which TurboTax does not support.
TurboTax has an arrangement with Sprintax to prepare Form 1040-NR for students and scholars. It might not be suitable for a "worker." Here's a question and answer from the Sprintax FAQs that lists the types of visas that it supports.
