Electrical help needed, underdash wiring is a disaster

Many ways to go, depends on budget, how original you want it, what your skill level/ physical condition, on and on
yup, i'm in the middle of cutting this in, in place of the stock fuse block. i'm lucky, the wiring is in great shape but the fuse block and bulkhead have issues. since i don't have to replace wiring, i don't need a kit that has flasher relays and all the other stuff built in. just cutting one circuit over at a time.
but if the OP isn't even sure where the problem is yet, need to figure that out first