Hi i think you need to locate one 100A fuse as close to the battery as possible.
Then the pair of 40A and the 15A at the distribution block is good .
Dont forget to also add a fuse for the display at the block.(unless fused inside computer)
To figure the gauge needed correctly i need to know four things.
#1 The power used by amps,computer and display
#2The distances from battery to the buss .
#3Then distance from the buss to both the amps and computer.
#4Finally the length of the ground cables .
I then enter the above info into the table for dc voltage drop .
The wire guage that will give less than 5% drop is correct for this application.