I got Jacks and Red Light Green Light a little further along. COP410 only has 32 nibbles of RAM: each of the 4 registers only has 8 nibbles; 0-7 are mirrored to 8-15. The code was treating RAM as 2 registers of 16 nibbles mirrored to registers 2 and 3. So only 1/2 of the locations could be accessed.
I'm not sure of the best way to do it, but I replaced the RAM_R and RAM_W macros with functions that modify the RAM index for COP410s.