The idea is fine, I did something similar, though my indicator lamps are wired the other way round. On my car amber was the pad wear warning and red is the e-brake and shuttle warning.
My VDO fuel guage had no provision for the low fuel light, so I used the amber indicator for that and left the red lamp as the brake indicator.
For your pressure switch sender you could tap the port above the oil filter and avoid the tee.
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