1. We have until 5:30 to finish this job.
  2. We have time until 5:30 to finish this job.
  3. We have time to finish this job until 5:30.
    Are all these sentences OK?

The only one which sounds natural is (1)

The other two are passable in one context.
Providing you mean ‘We have a period of time now in which to try to finish this job, however at 5.30 if we haven’t finished we will have to stop for the moment and return to it later,’ (2) and (3) could be considered correct, however theydo not mean the same as (1)