As for it irfanview also has the feature to aply an imported palette, but only in .pal format, it possible use these to apply the one needed by the game?
All palette file formats create the same image at the end, it does not matter to openxcom which program you use, as long as you use the correct palette.
OXCE rovides them along the executable so it may get the job done, right?
Yes, OXCE provides all palettes in JASC, RIFF and ACT format... all 3 work fine.