Alarm going off, car wont start

Hey yall, I drive an 02 325. I came home on saturday to my alarm going off in about 30 second intervals, tried starting it and it didnt even seem to be trying to fire. I opened the trunk to disconnect the battery and the alarm stopped, so I closed the trunk and tried starting it but got the same result. Then I disconnected the battery, let it sit for a few minutes, reconnected it and tried starting it but again nothing fired. Next day I had a friend come to jump it, and when we hooked the cables up the alarm started again. I tried starting it anyway and nothing fired. After we took the cables off the alarm stopped. I let it sit all day yesterday and went back today to start it but it was entirely dead.



I bought my car used and whoever owned it prior to me put in a speaker system and halos and I think they did some shotty work because I have a lot of random, fairly insignificant electrical issues that pop up from time to time. For example the back light on the dash and my passenger-side headlight doesnt work occasionally, my windshield wipers sometimes stop in an upright position, and my radio will cut out and only come back on after the car is turned off and turned back on. I know this a lot of information and a lot of it may be superfluous, but I figured the more info the better.



I'm in college so my car is in a parking lot and I have very minimal tool access so I'm hoping to get it back up and running without anything requiring access to many tools/a garage. Thank you in advance for any help you can offer.