Can'T see any problems or questions oO
You have to run the ADTs through OffsetFix, the should work afterwards.
Yes if you want to make custom intase or another stuff you need to make new wdt and then check the cordinates of adt's you can either keep the original cordinates and just adapt the wdt to it (simplest option) or rename the adts files and go from like 0_0 To 6_6 and so on, depending on how did you made the wdt afterwards just offset fix and everything is ready , Well it was for me atleast