[JWT4700]

Hey all. I need some help with my newly acquired e90. Had the 3 lights come on and had the below codes.
I just put in a new actuator motor (OE from FCP) changed the fluid (along with the diffs and transmission). Used ISTA to reset the new servo actuator and reset for the new oil. I did get a few errors “could not reset with our faults) I tried a few times, finally after deleting the fault codes I got everything to reset successfully! Test drive went ok… for 55 miles. Then they all came on again and it seems like the same codes. It was throwing cows as soon as i started it before, so having it go 55 miles was a little strange before coming back on.
My first question is can I replace the control unit with a used unit and just reset it using ISTA or does it need coded?

I did find water under the seat where the control unit it but I opened it up and it was dry inside.

Secondly I noticed that the car fax service history showed that the previous owner replaced 2 tires at a time for the entire time he owned it (12 years) currently the front tires are at 8/32 and the rears are 4/32. Could a life of mismatched tires taken its toll on the t-case? They are the same brand/model and size. I am getting 4 new continental extreme contact dws06 on Wednesday.

Going back to the water issue, there are two ground plates under the pass floor board, they did not have any signs of corrosion but should I remove them and look closer? Maybe I just have a corrosion ground issue? Kind of at a loss here and any help is appreciated!