2002 Chevrolet Monte Carlo electrical

OK so I am working on a 2002 monte carlo with the 3.4 3400 engine I changed the head gaskets manifold gaskets everything put it all together had starting issues hooked up a push button to it no problem. Ok had a misfire did all the normal tests to see why it was miss firing the lower manifold gasket ended up being the problem put the car back together. That's when my nightmare started oh let me back it up the ignition lock cylinder was going out as well it would take 5 mins sometimes to get the key to turn in the cylinder u really had to wiggle it and play with it to get it turn. So anyway I has to change that plus the ignition switch. Well Hugh electric problem first the battery won't hold a charge and really doesn't charge the dash lights go out really fast cause of the battery losing its charge I guess ever once and a while all the lights inside the car start flashing and going nuts and as they flash the speakers make noises in time with the flickering. Also it only happened twice but the fuse box under the hood where the fuel pump and drl relays are was making a loud clicking noise. Now after a charge the dash will flash a battery sigh low fuel sign and the security sign it will cycle between those 3 or sometimes it will flash battery low fuel security never seen that before also when I turn the key the furl pump doesn't turn on so obviously the car won't start. Please help by the way I have a good knowledge of car been working on muscle car a while just started on newer Cars a little while ago so the electrical and computer stuff is new to me still what a headache I also have a snap on Solis ultra diagnostic tool but the battery is too weak thanks for ur help