There is an ignition relay bottom left of fusebox labelled with a roman 1 here
https://www.autogenius.info/ford-transi ... x-diagram/ and I think you said you have already checked immobiliser fuses 32 and 33 ?
I assume being non turbo it has the bosch VE injection pump? if so look at the back of the pump just above where the injector pipes exit from the square iron section and find the wire going to the fuel stop solenoid(part no 240 here)
https://dieselcatalog.online/en/bosch/0 ... 14119.html (Hover mouse over to zoom in the picture)
and check that there is a +12v feed to the wire there with the ignition turned on, if there is power there then touch the connector on and off the solenoid spade terminal and listen closely and you should hear the solenoid clicking as it engages and disengages.
With +12v to the solenoid and the same to the starter solenoid it should turn over and start if the rest of the fuel system and engine are in good working order, which it sounds they are becasue it runs on easy start.