@ml37 It sounds to me that you intend to put several tool boards on a single print head. You can power them all from a single output on the tool distribution board, but don't exceed 5A total current from that output. Alternatively, feed the tool head power directly from the PSU, preferably through an inline fuse.

You can daisy-chain the CAN connections of the tool boards together. You don't need to feed them back to the tool distribution board. So maybe you don't need the tool distribution board at all.

What sort of print head do your have: a mixing extruder?