No you can't use that splitter to split the cables. That splitter is designed to also amplify the signals in it, from the computer, and since the use of the DB-25 cable was due to the large amount of conductors it has, it isn't compatible with any amplifiers etc designed for the computer serial/parallel cable.
A few members are also starting to use CAT5 cabling instead of DB-25, as it offers a much more rugged cable and more road-proof. Of course this will require you to make a converter box (Which is nothing more than a few pieces of wire), but you will end up with a more road-proof system.
It's not standard, but DB-25 cables IMO suck for anything that needs to be moved around alot.
You should be able to run the cable for a good few hundred metres, just keep it away from large mains cables. If you loose a small bit of signal thru the wire, the only decrease in performance you will see would be the output image size, and possibly the brightness in your lasers, it wont cause anything to corrupt/do erratic things (Unless like I said before, it runs next to power cables, which _may_ have an effect on it)
Hope I helped
