1. Yes, this is true. If it doesn't appear in the raws, it can't be changed short of memory hacking.
2. It has semi-decent explanations, but not good if you want specifics.
As for the sword thing...
DAMAGE:120 --> how much damage it does, of course. 100 is an iron short sword, while a long sword does more damage.
WEIGHT:70 --> this number multiplies how heavy a long sword will be depending on it's material density.
CRIT_BOOST:1 --> This has a higher chance to critically hit for bonus damage!
TWO_HANDED:6 --> If you are size 6 (dwarves are size 6) or below, you need two hands to carry this (though most often some creatures will ignore this)
MINIMUM_SIZE:6 --> The minimum size you can be to properly wield this weapon. Creatures of size 6 and above can pick it up and use it, but any smaller and it's hopeless. Not that the game cares half the time...
MATERIAL_SIZE:4 --> how many materials are needed. 3 is one metal bar, one wooden log, one stone, etc.
Any new items you mod in can most certainly be pulled out by an artifact maker. In fact, artifact makers can make stuff that their race can't even USE.
Any more questions are more than welcome, darling ^^
EDIT: I'd also appreciate if you PMed me if you have more questions. I'm a busy girl, and goodness knows I'll end up forgetting this thread if it gets swamped by more stuff! ^^;;
.. okay i'm just forgetful.