By the sounds of it, either your pump is knackered, or your inlet metering valve, or its clogged with dirty bits that got through the old filter, however
there is one other way i've found worked on a mondeo that I was having similar issues with, however I DO NOT RECOMMEND or SUGGEST using this method all the time, or at all unless as a LAST Attempt in desperation like now....
Get a CLEAN can of diesel, must not conatin ANY debris, (a thoroughly washed 2l drinks bottle is good for this) fill with extremely clean diesel, undo the high pressure union on the pump, not the rail, and undo the union on the rail directly in the top (its the pipe that goes to number 4 injector) use your priming bulb to pump fuel from the can into the injector union on the rail (you may have to improvise a connection onto the threaded union with hose pushed over etc to get a good fit...), and as soon as you get it escaping from the fuel pump union, continue pushing in with priming bulb, and tighten up the union. Now slightly open number 1, 2 , and 3 injector unions at the injectors themselves, and continue pumping until fuel escapes here with out any air. keep pumping and tighten all the injectors back up, then remove the priming bulb and re connect number 4 injector pipe. DOUBLE CHECK all unions are TIGHT. Make sure filter is full, and bled to pump as best as you can, then try staring.
AS said above, this is NOT a recommended method, nor guaranteed to work,
I take no responsibility for any muck / swarf / debris entering the injectors, its down to you how hospital clean your fresh diesel and container / primer pump etc is as to whether you introduce dirt particles to the injectors and kill them.
doing this removes most of the air from the high pressure side of the pump and fuel rail, and if the metering solenoid opens long enough to add a small amount to this when you first try cranking, you might just get enough pressure increase on the rail to allow the pressure sensor to keep the pump working, and force out any remaining air...
DON'T HOLD YOUR BREATH,it may not work at all, and you do this COMPLETELY AT YOUR OWN RISK, be careful....
best of luck,
Andy