What’s the best way to fix/clean up this wiring problem?

[Girth]

Solder and shrink wrap everything. Crimp connectors are a last resort. If you only want to wire things one time and not make the future you bang is head into a wall, take that advice!

You know, I used to do that, but gave up on it. A couple of broken solder connections on cars, and realizing there's very little solder connections in the aircraft wiring I deal with (high vibration, solder joints fail, or the wire breaks where it goes from stranded to solid/soldered)...... I crimp everything now. Two key factors in making that work. First, a GOOD crimp, not just a little "meh, squeezed it", using terminals that fit properly. I run non-insulated terminals and splices, of several varieties, and have several different crimpers to match. If all I have on hand are your typical insulated terminals you find everywhere, I cut the insulation off them. Second, adhesive lined heat shrink tube. Basically an environmental splice, the glue in the heatshrink tube seals it up nicely. It's usually a more robust heatshrink too, helps suppor the wire at the terminal connection.

For the OP..... what everyone else said. lol Figure out where all the goes, and either install some bus bars or an auxiliary fuse block. Better yet, I'd bet some of that mess is probably better off running off a relay. Great time to install a new box under the hood, to house the fuses and relays. If you haven't already, running your headlights off relays will help them work better and help your headlight switch last longer. Good god, fix those battery cables while you're at it. lol One of those bench mounted/smack it with a hammer, style of crimpers works OK for big cables, if you don't have access to the tools to crimp big connections. You can find hydraulic hand crimpers on Amazon and elsewhere pretty cheap these days though. They're slick, if you see a lot of big connections in your future.