I had water in the rear footwell of my 2004 Mondeo and was easily fixed. The water came in though the horizontal window weather strip ( where the window slides up and down ). Even a brand new weather strip will not stop all of the rain water getting in. It hits the SPEAKER and drops INSIDE the sealing rubber at the bottom of the door frame then fills the footwell.
All you have to do to fix it is to remove the door inner panel ( 5 minute job ) and with a hose pipe you will see the water dripping in above the speaker. I found a roll of 5 inch ( single brick ) damp proof membrane in my shed. This is thick plastic but any thick plastic sheet will do. I cut 3 lengths ABOUT 16 inches long X 5 inches wide. The speaker has 2 studs at the top. Make 2 holes the same width as these studs at the top of the three 5 inch strips.
Or just cut a fan shaped bit of thick plastic sheet 5 inches at the top X 16 inches down and about 12 inches wide at the bottom.
Remove speaker, then position the 3 plastic strips ( LIKE A FAN OPENING WIDER AT THE BOTTOM ) at the top of the speaker on the studs so that the water does not touch the speaker but runs over the strips like a raincoat and ends up on the outer part of the door panel and then drips out of the normal hole at the bottom of the door.
That is all I did to fix the leak on one back door but I am sure all doors can be fixed the same way.
You have to relieve spring pressure on the drop link so the bolt can be pushed out. Levering downwards is the only way to do that. Try it and you will see it will not damage anything. Obviously levering downwards with the bolts tight will break something.
I would phone the previous owner and ask where he got the injectors from because it sounds to me like one or more of the injectors have a leaking leakback valve so fuel pressure is reduced in the common fuel rail. Problem is it will cost about £450 to get all four injectors reconditioned as I did. But it did fix my cutout problems. You could do a leakback test on all four injectors, many web sites show how to do this using 4 plastic bottles.
If you look at the injectors you will see the leakback clips. Don't bother to try to take the plastic pipes off these clips as they will leak fuel all over the top of the engine. Go to a breakers yard or a Ford main dealers and purchase four new clips then you can make up a leakback test kit. You will need 4 plastic bottles + 4 new leakback clips + about 6 foot of plastic pipe cut into four 18 inch lengths. This is a standard testing kit they use at the garages. They quickly unclip the leakback pipes then clip on the test kit then start the engine and watch for which bottle fills up first then charge you £100 for doing it.