If there is no power getting to the inertia switch, it does sound like the relay. If the relay receptacle contacts are accessable, try bypassing the relay function. Have you already swapped the relays, to check the fuel pump relay?
That relay diagram above seems incomplete, or lacking detail. Usually you see four separate terminals, above shows the PCM connected to the main power load circuit. The PCM triggers the load, it doesn't supply it. You should be able to jump power to the wire going to the ineretia switch, but not to the PCM wire.
You can use a pin to jump power to the fuel pump circuit, but you must not accidently touch the terminal which leads to the PCM. The PCM is a low power component, it cannot take any full power on its many ground leads. Only do this if you can be sure to not touch the PCM wire.
The point here is to bypass that PCM ground triggering signal, and make the connection from battery to fuel pump. Note the wire colors above, remove the relay, and see if you can locate the main two terminals.
BTW, when you know that you do have power getting to the fuel pump, you can sometimes hit the bottom side of the fuel tank, and get the pump top trigger. If that happens, the pump is shot. Good luck,