Nasty scraping sound when decelerating

Tigger

So unfortunately due to weather yesterday I wound up hitting a seriously deep puddle. So now I get a nasty scraping sound from what sounds like the rear passenger side. Only thing I can think of is that the differential went. But it also sounds like a rotor scraping but ONLY happens on decel. A poster from an STI forum had an identical issue and found it was in fact the differential that went.

It is the 7AT. So if I'm in "D" and just do nice and easy driving and let the tranny do its own shifting there's very little sound. If I put it into "M" and engine brake it sounds ridiculously horrible and screams.

So the last thing I want to do here is get stranded on the expressway trying to drive the car to the dealer that is 20 minutes away. Unless someone can say one way or another or tell me that it should likely last for the duration of that drive... So maybe side streets and slow driving should do the trick.

Also, while I took it out for a test drive a little bit ago my gf pointed at the oil temp gauge and it wasn't reading a temp. The car was warm, blowing hot air, driving slow and it was 52 degrees out. The drive lasted 10 minutes. Got back and just as I pulled into the spot it climbed to 145 and quit. Checked the oil and radiator fluid. Both seem fine but my oil looked a little bubbly which is generally not a good thing but after it cooled a bit I checked it again and all was well. So I'm thinking water got in the ECU or one of the sensor plugs somewhere.

Anyone have any info, experience or advice here? It only has about 20k miles on it and not even a full year of driving on it yet. I'll attach pics below from my phone. I also found evidence of what appears to be something leaking on the passenger side exhaust pipe in the rear. Appeared to be melted plastic and at the last oil change the dealer said nothing about it. Now it looks even worse.

I'm open to any and all comments or suggestions but do not have close or immediate access to a lift. Thanks so much in advance for any information!!!