2001 BMW 325i Causing Hell...

About 2 weeks ago my car was slow to start. Then I tried to crank it after running into a store for 5 minutes or so and it wouldn't start at all, just a clicking noise. All of the peripherals like the radio, lights, etc. were working fine. Once I got jumped off I went straight to Autozone and they performed a charging system and battery check. The charging system checked okay (so the guy said), and the battery had about 515 cranking amps. I replaced the battery at his recommendation with a Duralast 49L. 2 weeks later and I had no problems until yesterday I'm on the way home and the battery light comes on a few times. When I got to the house I cut it off and immediately tried to power it back on and again just the ticking noise. It was late so I let it rest for the night. Turned it on the next day and it turned on fine. I let it idle a while and cut it off and tried to crank it back up and it wouldn't crank. I took a look and it seemed like the wires to the battery were loose so I tightened them up, jumped it off and drove around the block about 4 miles or so. The battery light came on intermittently and also the brake, dsc, and anti-lock brake lights came on intermittently too. When I got it home I just let it idle for about 2 or 3 minutes and without warning and without the temperature gauge going up it overheated spewing anti-freeze everywhere. Tried to pour more antifreeze into it and the reservoir seems to be broken.

The only thing I could thing is there wasn't enough power to cut the fan on? I had it serviced under 3000 miles ago at the dealer. It was frickin 2000 bucks and I don't have any cash to fix it right now so it definitely stays parked for at least 3 weeks.

What could the root problem be?