(Sorry - this answer got flipped into a comment, so put it back; i'm new to this forum)
You need to dive into the 'address' of PLC5 comm block. I haven't worked with this for 8 years ... but in your SLC message block, you should be able to set up some COMM info - like a slave address.
If you look here, you can see this from RSLgx-5000 view-point, but will be similar to PLC5.
Again, my old brain is fuzzy, but on the comm tab you have the 'dst link' and 'dst node' settings, which default to be treated by the IAP as Modbus address 1 (aka: your first table entry). Try putting 2, 3, and 4 into the appropriate 'dst node' ... and if memory serves me, this will cause the IAP to use each of 4 entries.
Adding - if your RSLogix MSg block offers 'local' or 'remote' addressing, pick local, as then I think it only asks a DF1-like SRC & DST info. You want the DST. The 'remote' should still work, but it is DH+like and more complex to set.