Electrical Problems! HELP!!!!

[lsu_beaux]

Im not sure where to begin but here goes nothing, Ive been having problems starting in the morning for a couple of days and Ive had to get jumped off, well the first time someone jumped me off it ran pretty smooth but I gained door chimes. Ive havent had door chimes since the install of my kenwood DDX719 (which ive had for almost a year now) because I told the guy installing it that i didnt want them. Well i went to autozone and they checked my battery and said it was perfectly fine, well it wasnt, the next morning i turned the key and it made the clicking noise, and i got jumped off again so after class i went back to autozone and they checked it again and said it was bad so i bought a new battery. Now the initial start up is fine but idle isnt. Itll settle at about 500-600 for a second or so then drop down to 200-300 and shake. 2 years ago i also installed flex-a-lites electric fan kit and now its not operating properly, ive never had an issue out of it before other than it blowing fuses because i install too small of a fuse. My vehicle is a 2003 Chevy Tahoe z71. Any help is much appreciated! Thanks!
Forgot to add that my check engine light came on and when i ran the code it was for both knock sensors, i dont think that would effect anything but then again idk