When using selectors, all of the arguments go between the same pair of square brackets and are separated by commas. What you wanted to do is probably this:
testfor @e[type=PrimedTnt,x=-272,y=58,z=-1844]
You're getting the error message because you've made [x=-272 y=58 z=-1844] an argument of its own, not part of the selector. As it happens, the second argument for testfor is NBT data. The correct syntax to specify NBT data would, as the answer above says, be {x:-272,y:58,z:-1844}.
HOWEVER no entity has an "x" int, a "y" int, and a "z" int in it's data. Although it's the correct syntax and won't cause an error, it will never match an entity. The correct tags for specifying location with the NBT argument would be this:
testfor @e[type=PrimedTnt] {Pos:[-271.5,58.5,-1843.5]}
The chances are you didn't want to do that though, as it'd test only for that very specific point in space and nothing else. The solution is the first command I gave, where all of the arguments are in the square brackets.
As MrLemon has pointed out in the comments, there is an error in your fourth step, where the command is:
effect @a[score_nightVision_min:1] 16 30 0 true
You have to replace the colon ( : ) with an equals sign ( = ) for that part to work.
Best Answer
Once again, you have put a space in between the
@aand the radius selector.Correct command:
/testfor @a[r=5]A redstone comparator coming out of the block will emit a signal when this is true.