We're under contract with a home remodeler. 80% of work is done but now haven't heard directly from the contractor in 2 weeks. What to do?

Is the  contractor relatively local? If so, you might try simply driving over to his place of business--it's hard to ignore people standing in your office or at least on your doorstep.

To get information, if the home remodler has been using any subcontractors, you could contact them directly to ask what's up.

It is flu season--two weeks is annoying, but not unheard of, for no communication without any other problems or issues. If you take reasonable steps like the above and can't get an answer, then you may need to start contemplating legal action--if people do not honor commitments, that is, in the final analysis, the only way to compel them to do so.