Electrical problem 2000 Honda Odyssey

2000 Honda Odyssey.\R\nThe passenger side headlamp burned out and I replaced it, no issues two days ago. Battery was cranking slowly and terminals were corroded so I cleaned them. Last night in 15 degree weather, engine off and vehicle parked, horn stated blowing without a known cause. I could not start the vehicle so jumped it while horn was still blowing. It continued for twenty minutes, then stopped but vehicle would not shift out of park. Horn does not work now. I do not know where the fuse is. Owners manual does not list it. I used the key and pressed the shift lock release which allowed the vehicle to be driven. When I went to shut off vehicle. IP lights, running lights stayed on even after ignition off and light swith turned off. I disconnected battery and now can start vehicle without problems except I still need to use key and press shift lock release. I suspect I need to replace brake light switch on brake pedal to fix the shift out of park problem. Does anyone know if IP lights and running lights stayed on, horn staying on, replacing headlight, cleaning battery terminals, disconnecting battery are related. When it rains, it pours. Help.