New to X5 world, advice needed please (Cooling and fuel pump)

[Aidzer0]

Hello Fellow Outposters!

I have been in the BMW world for a while, I've had my e46 for 3 years now, did all the work on it myself, Gaskets/seals, manual swapped, cooling overhaul, steering overhaul, electrical gremlin squashing, DME/LCM/TCU coding etc.

Recently I acquired an X5 (2006 4.4l N62 with 302k KM mileage) for my wife, I have done a fair share of research prior to the purchase and most of the critical engine issues were done, the coolant return in the valley pan was fixed with the bimmerfix stent, rear air suspension replaced, all the brake lines were replaced, most of the cooling components were fixed too, and NO SMOKEY EXHAUST!! (Valve stem seals were done too)

TL;DR: Is Delphi fuel pump good? And P/O used Delphi temp sensors, should I get OEM ones with the T-stat I am getting?

I am about to order a delphi fuel pump and Mann filter (The pump is whining and has 302k KM on it...). Seems to have outlasted any BMW pump I have ever seen... This is where I need the first set of advice, Is Delphi a good pump? FCP only have the Delphi or OE BMW which is almost double the price.

The next issue is an interesting one, the P/O did a somewhat cooling overhaul, water pump, hoses, 2 sensors, Expansion Tank, and one of the things on the list was the Dual temp sensor (13621703993) and the fan switch (13621433077, on the lower rad hose), the car is not reporting the correct temperature and seems as though it is not getting to temperature correctly (The fake gauge goes to HOT then comes back down in seconds), I have the thermostat in mind, and I will be replacing that (the P/O did not use OEM or OE parts. Both of the sensors are Delphi from Rock Auto.
The car is spitting out a code, P112B - Engine Coolant Temperature Sensor 1 Minimum Temperature Implausible, which tells me that the T-stat is stuck open along with the sensors not working.
When the code appears, if I power cycle the car, it will not crank the engine, until the code is reset. The car runs fantastic and there is no sign of over-heating.
Am I correct to say: I should get the 2 sensors listed above along with the T-Stat? or just the T-Stat?

(I use OBDFusion to read codes, no other issues are present, just the gauge being weird and the code popping up very randomly, I would use my INPA and/or Scanner 1.4 but I do not have access to them for a while)

Any and all advice is welcome, please don't tell me I am stupid for buying a 302k KM BMW, I know it will require work, I just want to learn the car, I love working on cars and I know they can be reliable with enough effort and money...

Thank you!