Hmmm, it doesn't actually say they're the mist type jets, hopefully they are as if they just give a single jet then it's not an upgrade.
https://www.ebay.co.uk/itm/Volvo-740...e/292670134756
That's the non-return T-piece valve, it will dribble all over the dizzy cap with the bonnet shut - don't forget it moves forwards as well as down when the bonnet is shut! It's designed to let water out when it fails - maybe your jets aren't blocked after all?
Looking at your earlier pics it seems the headlamp wash is indeed disconnected. The low fluid sensor/switch fits in the smaller of the two holes on the top, the large hole has a rubber skirt that also fits round the fill tube, the smaller one had a screw cap with a hole in the middle for the sensor.
Gives you an idea!
As for your warning lamp, it's something to do with the braking system, possibly needs bleeding, low fluid level or something of that ilk. Does it have ABS at all?
The low washer fluid warning light is on the left of the row of warning lights at the bottom of the instruments. If memory serves it's to the right, next to the ABS warning light in this shot :
It won't come on though as the switch/sensor is disconnected - it may show up on the bulb check function when you first switch the ignition on.
