I redumped Boku Dracula-kun and the current code produces the proper dump. My standalone Famicom reader dumped the cart without a problem. It took a few tries using the FC-SNES adapter with sanni's Cart Reader.I have a copy of Wai Wai World 2 on the way. I'll check it once it arrives.
No, 27c256 can't be programmed with the Cart Reader. Only 29F080/16/32/33 flashroms are implemented for Gameboy.