1996 Nissan Sentra Car Stall. Won't start

Electrical problem
1996 Nissan Sentra 4 cyl Front Wheel Drive Automatic 70k miles

My car stalled after hitting the curb with the front wheel. When trying to start the car again, there were no cranking noise and I heard a click along with something that is trying to rotate (starter?). I could see my air bag light blinking when keyed to the ON position. It turns out that the battery was dead. I replaced the battery. I drove the car couple of times the first day. After two days, the problem occured again. I wasn't able start and when I try to start the same thing happened, no cranking noise, a click on the ignition and something under the hood is trying to spin. I checked the voltage of the battery and it was low about 10V. After a couple of try, the battery was down to 9V-8V. I tried to jump start but no luck. What could be the problem? Ignition switch? Starter? Alternator? Fuse? Fuel pump? Distributor? Maybe the battery just doesn't have enough juice to crank the starter?

One other thing is since the engine light was on, the code was P0505. IAC/AAC value? Does this affect the problem?