04 VW Jetta issues!! Please HELP!!!

Ok after changing the guse box on top of my battery, (also changes spark plugs and wires at this time and did an oil change, and topped off fluids and checked fluids) changed my battery completely thinking maybe a cell drying up. Have check every fuse on main fuse box, bought a dianostics code reader. (Got ccm = convenience control module. Called places like our local auto zone and what not they all tried telling me ccm is same as ecm= electronic control module. This is the main brain basically and pretty expensive. So i kept looking lol.) Husband hooked my stereo up a month after getting the car. There was a wire he wasnt 100% sure about but come to find out this wire was my problem. It was a brown wire. That when he contect wire to his testers it was registering 4.9 volts. That being connect to stereo. And then u using a window switch or lock switch (we are assuming all this. We are not machanics or licensed at anything lol) that it may have cause the fuse which we also had a very hard time find blow. Its a 20 amp fuse that is under ur steering column. That all the plastic and metal plates off. Look to ur left a bit and there is the other fuse panel. It has a 175 relay fuse u will see and 3 fuse slots (with fuses obviously) and it was the 20 amp fuse blown. Now my car locks properly (before i would kit lock on key fob it would do a half a$$ honk but doors could still be open and mo alarm would go off. But pop ur hood and alarm would sound lol) hit lock inside of car door and still doors wouldnt lock acted like they wanted too but wouldnt. Windows wouldnt roll down. The switches for gas tank and drunk wouldnt work. The interior door light wouldnt work. And it had even caused my car not want to crank. It would do the whole turn over crank for a maybe 3 sec and cut off. But now EVERYTHING works just as it should. Hope this may help someone.