2006 Convertible - ABS, ESP, BRAKE light on, no speed odometer
 

Help me please!!!
I have a 2006 convertible! About a month ago all 3 brake light came on and it died in a Chick'fila drive thru. No power. National Tire and Battery (next door) rescued me and ended up changing out the alternator (said it was bad) then said the battery had a bad cell (changed it out). All good for about 2 weeks. Then the alarm went off while I was driving, sitting through red lights, etc... made it home, and noticed one of the battery connections was totally locked up and no way to tighten to the battery. Changed out the battery connectors. All good until today.
Back to square 1....all 3 brake lights came on, speed odometer went to zero, but it did not die on me. I managed to drive it home.
Once I killed it, it will not start again, or even turn over, but the light are still coming on, so I don't suspect any battery issues!
My back window does leak into the trunk, but I try to keep it dried out.
Any ideas or recommendations????