The 68000 cannot connect directly to the RAM. 68000 bus cycles and DRAM bus cycles are not the same.
An interface chip must be used. These were mainly PAL/PLD chips with the logic written by the board vendor.
Most 32-bit 680x0 chips have the full 32-bit address bus which give access to 4Gbytes of address space.
However to save money very few board designs forward all address lines to the RAM sockets.
It's not a matter of passing all address lines to the RAM. The board does some address decoding also.
While a worthy home-brew project I feel that with the lack of documentation you might never be able to work out how the logic on the board works.
