aux fuse block hellpppp needed

ok so i have done research and used the search bar and read countless posts but still have questions....

1. i need to extend the positive cable from the factory fuse box to the positive battery terminal in order for there to be slack for my optima. can i run 4 gauge or does it have to be factory size. 1a- if i go 4 gauge do i have to mess with the ground for the negative battery and make that 4 gauge as well?
2. when i add the blue sea I'm going to be running 4 gauge from battery to the circuit breaker(100amp) and from breaker to block, also 4 gauge from blue sea to that ground bolt near battery, sound right?
3. when i add my power cable for amp(4 gauge) can i run that wire off the exit side of the circuit breaker? the inline fuse for my amp is a 140 amp i believe

not amazing at electrical stuff but i wanna make sure just putting a 4 gauge to extend that section is gonna hurt anything

any help is greatly appreciated just looking to not blow shit up

 

1. I believe 4awg is actually bigger than factory, so you should be good there. Certainly looks bigger. Just be sure to use pure copper. OFC. none of that CCA crap. aluminum will do nothing but hurt you.
1a. Yes, you definitely need to upgrade your factory ground from the chassis to the battery with matching wire
2. yes, 4awg from battery to breaker, breaker to blue seas. and 4awg from blue seas ground side to ground bolt you mentioned, although I personally went straight to the negative battery terminal.
3. Definitely do NOT connect anything else to the breaker. Your audio amp needs its own fused connection directly to the battery. (if it has a 140 amp fuse, you actually need 1/0 awg wire. 4awg is only safe around 100 amps. Also in this scenario, you need to upgrade the wire from the chassis ground bolt to the negative battery terminal to 1/0 awg instead of the previously mentioned 4awg

 

I ran the 4 gauge wire w that 140 amp before with This system no problem. But your saying in order to upgrade just the wire between the pos terminal to the stock fuse box I also need to upgrade the ground battery terminal to match the 4 gauge?

 

I certainly would. Having 4awg power cable doesn’t give you any benefit of you still have an 8awg ground cable.