1, 2, B, C are correct.
3 on the pushbutton should go to 6 on the rotary board - R51 to pad Y.
12 on the pushbutton should go to 9 which is connected to pad X. These latter two are for the +4 setting so they need to connect to the output on the line amp.
4 goes to 4 = ground. Correct, but the designations are confusing since there is also a pad 4 on Jakob's layout.
A goes to A = pad 22 which is also point 22 on the schematic. So that is also correct.
?a therefore should go to rotary pads 2 or 3, which goes to pad 4, connecting to the ratio switch common or GRN on the original schematic. But since pad 4 on the meter board just goes to pad 4 on the ratio board, just wire it directly to the ratio board pad 4. It should probably be shielded with the shield grounded on one end.