You’d probably need more fuel than 10l to rule the transfer pump in/out, they have large tanks, and you would need to fill it over ‘the hump’.
I would first change the fuel filter and prime using the correct method… see @Arctic2 write-up and...
Update.
Fluid from the exhaust drip int diesel an the expansion tank is empty.
Best hopes are it's just the head gasgit.
Is a right sod, all the way to St Ives an back fer pasties wifout a blip anorl..
A second key is useless while the vehicle is immobilised cos the BCU is locked for programming, you have to remobilise it first then a good used key can be programmed with nanocom by a friendly member close to you or you can hire one HERE ...or...