Recommended connectors & crimper tool for custom length jumper cables?

Screw that. Use CAT5 Strip the outer insulation and separste the wires.
You can still use any connectors yiu want but CAT5 allows you to make cables anh length ( within reason) I have one of those crimping tools. It's a cheap Taiwnese clone of the crimping tool for crimping gold RC servo ribbon cables . It works perfectly but has no Make ir Model # becausd it's a clone. The gold connectofs slide into the three pin black connectors that plug unto RC receivers, like the ones on RC servos. I buy tge connectors at the RC hobby store (Brand is MPI). . I don't order tgem from Digikey because the stire is on the way to work and I don't have to wait.. I could give you the MPI part # if you want look it up. I'm pretty sure the CAT5 wires will fit in the connectiors.