If you want a smart, over-complicated solution, might be worthwhile to find hobbyist electronics forums and asking questions. Look up the table on 9-33 and look at the resistances and then take that info to the forums and look into threads where someone made a warning light for a certain voltage value over time.
Something like this: https://forum.arduino.cc/index.php?topic=183046.0
For an analog low fuel light, you could use the following:
A stranded length of 24 gauge wire (think that's the OEM gauge, that's what my wire strippers told me, anyway),
Connector pins for said gauge,
an "'X'-Volt opening" diode,
an "'X'-Volt" LED.
How to do it:
First, you need a value of voltage value between the "send" side of the float sensor to ground at a particular level. The manual specifies a float point of 2.22 inches for a particular resistance reading, so I deduce that that fuel level is "low fuel" and the light comes on in an OEM gauge cluster, so let's just round it to 2 1/4 inches. Measure the voltage at idle, 5000 rpm, and maybe 8000 (shouldn't rev higher in neutral) with the fuel at 2 1/4 inches. Average that reading.
For the purposes of simplicity, let's say that the average voltage reading from the "send" side and ground at "low fuel" condition is 4V.
Time to make a low fuel light:
Connect a length of wire to the "send" side of the fuel float sensor output.
Connect the other end of that wire to the NOT STRIPED end of the diode.
Connect another length of wire to the STRIPED end of the diode and the other end to the LED.
Connect the other side of the LED to ground.
What will happen is that the resistance on the float sensor will lower as the fuel gets lower. Once the resistance drops enough, there will be "X" volts between the send side and ground. For the sake of simplicity we called it 4V. If we bought a 4V diode and a 4V LED, whenever the voltage output of the float sensor hit 4 volts, the diode will allow current to pass and it would light the LED. If it flickers, that's fuel sloshing around. If it becomes steady, you are below 2 1/4 inches.
Note: most LEDs are rated for 5V, so finding a "4V" would be difficult. Using a 5V LED just means that it will be dim at 4V. Maybe using a 5V diode with the 5V LED would give you more warning for low fuel since the resistance of the float decreases with fuel.