big 3 problem not the normal 2005 grand

Hey all,I hate to start out my first post with a long question, but I really think I screwed myself this time. I have a 2005 Grand Am base model and I have attempted a big 3 upgrade w/ replacing the factory wires (mistake.....)...I ran a 1/0 gauge wire from the battery to the fuse box under the hood, replacing the 4 Ga. factory wire. The factory terminal had 2 positive wires coming from it. One for the fuse box and one for the alternator (or so i though). I could not locate where the second wire went but I could get a power reading at the alternator wire when I placed the second terminal wire on the battery. Hence my thinking it disappeared under the engine and reappeared at the alternator. So I though I could remove the wire from the alternator and not have to be bothered with the other side and just tuck it away sealed off somewhere. sooo....I replaced the 8 gauge alternator to battery wire with a 4 ga and used a 120 amp breaker at the battery (mistake #2 I keep blowing the breaker).The ground terminal had 3 wires 2 8ga. and one 22ga. One went to the chassy, the other to a location unknown. These wires ran through a inductive trigger of some sort. I removed the chassy wire and cut the 22 ga. and linked into the new terminal and left the other engine ground unhooked as I would not need it with the wire upgrade. I ran 1/0GA from the battery terminal to a 2 legged body ground I fixxed to the sheet metal on the firewall (cleaned bare under the legs) and ran 4Ga. from the terminal to an engine ground on the alternators case that also grounds the engine. I also ran 4Ga. from a bolt on the transmission to the chassy with another 2 legged grounding block. At this point the car would run all electronics with the key on, but would not start. I then discover the red wire I have tapped off and tucked away was for the starter (battery--->starter----->alternator) and I have no room on my new terminal for another 8Ga. wire. As I have a 4Ga run for a 1000 watt kicker mono block in the trunk. To test the circuit I re-connected the wire I removed from the positive lead on the alternator and the car started. So Now I have a live 8ga. wire tapped off and tucked out of harms way.... and I'm not happy about it.... but until I can track the wire down all the way top the starter, I am stuck with it.Also the inductive pick-up (I have learned) controls charging to some extent and now I am thinking the 1/0Ga. wire ran though the pick-up might not be a good thing. It should be the same amount of power though the cable, but I don't know for sure.I have a terminal that displays voltage and when the car is started it hit 15.4 volts at the terminal.... I am thinking the alt isn't regulating charge due to incorrect values from the inductive pickup (isn't the alternator regulator a off/on type of switch and not a true voltage adjustable regulator?).... or the cheap e-bay terminal isn't reading correctly.Also I have to remove that dead second ground wire from the car, but right now it is taped and tucked away. I hate doing such guess work but I could not run my system without horrible lights dimming and even some poor engine performance from weak spark. I read and re-read all the posts I could find about doing a big 3 upgrade and I have yet to see anyone run into these problems. Any help would be welcome and yes I understand I have a lot of learning to do when it comes to this..... the 120 amp breaker will tell you

There is no need to REPLACE all of the factory wiring in place. You should have just left it all there and just added a straight shot from the alternator to the battery and just add ground wires.

can you not replace all of the original wires back??? then see where it sits at