I'll dump you a copy of the DMS2000 prom, also the DMS PC card prom. I’ve even got an 8086 DMS unit; I’ll get the prom from that also. I have disassembled a lot of the 2000 prom and most of it, including ports, matches the DMS-3 prom. The main differences relate to banked memory, memory testing and hard disk code.
The 2000 has an OMTI-5000 series controller that is compatible with the Xebec 1401. Connected to that is a Rodime hard disk, but it appears someone attempted to wipe it. I’ve managed to dump the complete content of the hard disk, but large swathes have been replaced with blocks of 0xF6 (blank formatting?) which unfortunately includes much of the boot code. Rummaging through the hard disk dump though, I have found several copies of ZCPR with BIOS for the 2000 – I was really pleased to find my disassembly of that bore quite a resemblance to the DMS source you now have on-line. If it comes to it, I’ll use that to recreate a CP/M boot disk.