I have not got one of them on my 2004 90XS

I could understand a restriction to keep oil from draining quickly after stopping to aid cooling and lubrication on rundown but not a restriction to feed oil in.

If you do not have a filler strip fitting tool, I used one of these to fit the filler strip when I replaced my seals, nicked it out of wife's draws. Which was a strange place to keep it.

You could always email Uncle Mike, (put a link to your thread in email) have a look at one of his wiper videos.

Does the alarm still activate with all the interior bulbs removed, if not its a quick fix until you find the fault.

Good point about loctiting the bolt threads, mine slackened off over a month or so and I know there were tightened down.

Putting it back in is when you may struggle, you may need to prise the chassis rails open a bit with a block of timber or use a even bigger hammer. (Actually mine was not too bad to take out or put back)

Watch this, he had same problem and changed his motor and problem still there. Then cleaned his wiper stalk contacts to fix the fault, on a disco but hay its a Landrover.

Stalk switch

If its turning over ok with a good battery its usually fuel related if it won't start. Pull the delivery pipe off the fuel pressure regulator and see if you are getting fuel there. Crank shaft sensor fault/connector is another possibility

It has the self park switch, its the bit with the X on it.

You can replace the self park switch on the wiper motor very easily, a new wiper stalk switch would be a good idea too and not very expensive.

Watch this video, you may have a similar problem.

The only other place I have seen the OBD socket is under the passenger seat on front edge of the battery box, as on my 2004 TD5.

Are you using the correct wheel nuts for alloy wheels, wheel nuts for steel wheels should not be used with alloy wheels.

Get the wheels as well. https://www.ebay.co.uk/itm/Land-Rover-Defender-Boost-16-Alloy-Wheels-With-Continental-235-85R16-Tyres-/124574581167

About 2 minutes 30 seconds into video, Mike give a hint to clunk.

Also ensure the trailer weight is biased to the front of the trailer, which will put weight on the real axle. Never load the trailer to take weight off the drawbar.

Might be worth rechecking the injector seals, did you use genuine copper washers, many of the after market washers are just copper coloured steel washers and do not seal. Check for small leaks on the fuel pressure regulator. Last year I had a leak on the fuel filter, it never leaked fuel out...

20k, 20k, run for the hills, he is asking far too much for it, walk away and keep looking for better example and cheaper.