Sniper and Trunk Battery help

Wow. Thanks so much for the insight and help! Not calling out Crackedback at all. Been doing lots of research on this topic and I thought he seemed to be the most knowledgeable about it and when I saw his diagram I went with it.
I wasn’t sure about the EFI comparability which is why I am here asking the experts. The Painless relay came with 8 gauge which I thought was suspect. The 18 gauge wire to be placed on the opposite side of the switch seemed sketchy as well.
My ford style relay part number ST85 is a continuous duty.
Is the consensus that I scrap following this diagram if used in conjunction with EFI or move on to something else?
I’m not opposed to changing at all just now I’m not sure how to lay it out?
Thank again to everyone. Learning every day on this