1) Most Seymour Duncans come as a 4 wire conductor which means, yes, they are more work than a single coil, but by very little. Really there are only 2 extra wire that you need to worry about and SD provides a schematic, very easy.

2) Yes, if they are 4 wire conductor then they can be split.

3) They have the same output as an actual "double coil" pickup would have. The only difference between these sized humbuckers and a "regular" size humbucker is in fact the size.