To me it seems like the recommended EPR settings from the docs at Avsim (http://library.avsim.net/search.php?SearchTerm=Boeing+707+Operations+Manual&CatID=root&Go=Search) can't be applied here, otherwise you'll never get very much above V2+15 even on light loads.
We have to ask for the source of the docs of course, but this looks trustworthy for me.

Going full throttle isn't the best idea too because she easily breaks the 250kts limit then, so you'll have to look for something in between.

As I assume from the startup process, where you start the fuel and see a "bam!" on the engine readings when they light up togehter with a very fast engine start procedure overall, these are again FSX SDK related engine models (like all Captain Sim releases so far) and therefor not the ones to be called extremely accurate.

I can live with that although I would appreciate a more realistic model.

On the 727, I had to edit e. g. the available thrust values as they were too low for the engines on the mid and later 727. Otherwise especially the 727-200 dies on high loads.
Might be that someone has to look for the 707 too.