Cadillac Forum - Enthusiast forums for Cadillac Owners - PLEASE HELP: P0420, P0449, P0463, P0741, P1189, P1860, U1000 2000 DeVille

I'm new here...name's Lia I have a 2000 DeVille with 234,065 miles on it(its' paid its' dues, I know) that is currently reading the following codes:

p0420 Catalyst system efficiency below bank #1 CURRENT
p0449 EVAP purge/vent solenoid CURRENT
p0463 Fuel Level Sensor High Voltage CURRENT
p0741 TCC Stuck off CURRENT
p1189 Engine Oil Pressure Switch Circuit CURRENT
p1860 TCC PWM Solenoid Circuit Electrical CURRENT

And also:
AMP U1000 Class 2 Communication Failure
IPM B0249 Heater/Defrost/AC Door Range Error (probably why my A/C doesn't blow through the front vents?)

Recently replaced the radiator, thermostat, and surge overflow tank + Idle Air Control Valve.

When driven on the freeway, it struggles to kick into overdrive. It's also dies almost every time I come to a stop, even if I keep my foot on the gas while stopping. It starts right back up in neutral with no problem. It runs rough with AC on, but smooths out a little at night when I drive with it off. I've changed the oil, but the DIC panel still keeps telling me to check oil level, even when I manually reset it(EOP pressure switch circuit?).

I know the Catalytic Converter needs to be replaced, the EOP Switch Circuit needs to cleaned or replaced, and the TCC Solenoid probably needs to be replaced. I'm by no means an expert, I just wanted to provide as much info as possible, so I could be provided with accurate feedback.

Also, for a few months now there has been water(not moisture, they're actually saturated) in the floorboards of the car. Since we've been in a drought and I park under a carport, I know it's not a windshield leak or anything like that.A couple days ago my battery died and I opened the compartment under the backseat to check it out and noticed that it had about 2" or of water in it that the battery is sitting in. The water isn't touching anything on the battery but the casing, but I still thought it was cause for concern. I have no idea where the water could be coming from or where to even start looking. The best way I can describe the water is that it's not pooling (as in a couple inches or more) in the floorboards, it's just saturating the carpet, but it is pooled in the battery compartment.

Anyways, Thanks in advance for your help
Lia

P.S. Anyone know why my mirrors and seats reset every time I turn the car off? It's very annoying