Matt Zagoren is the guy offering some free docs for all sorts of planning purposes. I think the files are called 707perf.zip. But be aware that you can't give much on the EPR readings with FSX default engine models. Those will be off by large amounts, while the N1 sort of comes closer to the charted values.

Not so much a flaw of the 707, but of the FSX background. Only a dedicated and custom engine model could help. But the fuel planning and things works pretty good. You may see the sim showing slightly lower values though, so you may receive some more range than on the rw bird.