Hi, Komninos, wasn't mistrusting you really just didn't wondered where it was going to want to extract to but browse function makes it OK.
Silver Rusher is right that you will definitely have problem with that large a sea area on that size map, see:
https://forums.totalwar.org/vb/showthread.php?t=66332
for some research and experimentation with that.

the mod Silver Rusher mentions in that thread is the closest one I've seen to what you were aiming at (the Crusades) but they say that they had to reduce map heights down to 521 x 591 and its also got more land.
https://forums.totalwar.org/vb/showt...t=61093&page=3

If you want to test out that other files are working take the ports off map_regions rename / backup your map_heights and make a replacement version that is right size and flood fill with RGB 1,1,1 'black' so all is land - so temporarily eliminating land-mass ratio problem. That will let you test out that your text files are working.

P.s. I'm not sure if for that size map you might also meet a problem on the maximum size of a region (thought I had a flaw with that once but never really tested) - I've normally use a few more provinces since just in case.