Clavurion

You only need that driver seat module (PM-SM).

Key remote function has nothing to do with immobiliser which is just passive chip in the key. So these are two separate issues. With diagnostics you could check if the reason for not cranking is immobiliser (key or EWS module). Body module (GM) is responsible for central locking features.

Sounds like very poor quality. Get Lemförder this time.

What kind of failure did they have? Worn ball joint, perished ball joint rubber or damaged inner rubber bushing?

Y Yes. The one for rain sensor option has rain sensor lens glued on the windscreen from factory.

You can drill a new hole thru that plastic from cabin side. After you have guided the wire thru seal it with butyl sealant.

If DSC light is constantly on there must be a trouble code with proper tools.

Fuse for fuel pumps F22. Fuse for fuel pump relay F31. Fuel pump relay: green relay behind glove box.

When is your car manufactured? Can you see air bubbles in the engine bay clear fuel line?

How much fuel in tank? If level goes under ~1/3 it will starve if in tank pump has failed. Both pumps are activated with same relay and supply from same fuse. Pumps are activated when ignition turned to pos. 2 and stay activated for 60 seconds if engine is not started.

Not that difficult to flush all oil thru oil cooler line. Drain oil going from cooler to gearbox, run engine and constantly fill oil sump with fresh oil.

Because BMW doesn't put effort to think what happens to the vehicle after ~200 tkm. The gearbox will last (or not) until there regardless of oil changes. The oil change would only make the estimated service cost look higher. Of course real life is different if you care that gearbox will last longer and work properly on higher miles. My E39 530d (mapped) has now nearly 400 tkm on the clock. It still has original GM gearbox working as it should. Oil has been changed every 120 tkm and I also renewed the torque converter (preventative) on 300 tkm as this is the weakest spot on these GM boxes.

Actually Mahle (Hengst, Knecht) makes the ones that used to be OEM before BMW changed to Mann. I also prefer Mahle oil filters as Mann versions have so stiff center part that it always feels like filter housing is going to snap before the old filter is removed.

Mahle LAK 73/S. I think it has a much better housing than original/Mann.

Vacuum pump does not affect CCV. What do you regard as very high mileage?