I haven't really played around with the globe much, but just changing the countries' funding and areas shouldn't affect much beyond local score and council income, so you should be reasonably safe.
Playing with regions and terrains, on the other hand...
I don't really recommend pooling so many countries into one block, since if the aliens infiltrate that (and the increased area also increases infiltration chances), the player's financials get a rather rude cut.
The date is just cosmetic.
If you had a million MiB bases, these could have eaten your score by themselves. The other stuff indicates you did things without really understanding what exactly you were doing.
I don't think there's a magic method for even an experienced modder to assure you nothing will ever go wrong based on just one part of the changes. This is a complex game, and even ten lines of code can sometimes produce surprising results.
