Hi. Do you still need the compressor/decompressor? Two weeks (or so) ago I coded simple compression/decompression utility for my friend (rle+lzss). It works just fine with type1 compressed files. I have tested it with FFX (PAL) and FFX:International (jap/eng). I unpacked scene files for a dozen of locations, changed the text, compressed the files back, inserted them into image and played the game without any problems. So I guess it should work quite well. If it doesn't, I'll fix it whenever I'll get the chance.
I've just uploaded the file on rhdn, but it will take some time for it to be accepted. Here is the temporary link: http://www.okami.pl/down/ffxtool_01a.zip
There is only one thing I didn't test properly. I'm not sure, whether the maximum run length is 259 or 515 bytes. But if it was 259, then 0x7f value would be somehow reserved, which would be quite weird (couldn't find any original file with that big run). Though, if it is reserved for anything else, I wouldn't be that much surprised (I'm working on FF12 now, which I coded entire and complete toolset for... So I DO know that S-E is sometimes a pain in the ass).
PS. There is an error in the sample files you've posted in the first post. Either the emulation was not perfect or you screwed something up with the memory dump (or you dumped it at the stage, where some parts were already modified/overwritten).