your power wiring sounds good.

your 'sensor grounds' are grounds for the sensors themselves, they're provided by the ECM and noise filtered or referenced or whatever. they don't connect to chassis ground. don't use them as a ground except for with sensors as intended (in all seriousness, seen that fry an ecm)

in a factory configuration; two of the ECM grounds end up at the coil 'stud' (red 18 and blue 1), and the other two end up on the passenger side engine block (red pin 2 and grey pin 32). i imagine the block ones are the low noise, due to distance from the coil, and the coil ones are for high load? who knows.

i've grounded them all to a common ground block on my car, then the ground block to the accessory bracket with welding cable. never noticed a difference. my car runs perfect and all my signalling seems clean.