Update:
So equipped with a better soldering gun I re-did that splice as well as most of the others both under the passenger and driver's seats. There were a couple I left alone because they looked fine. The ones under the passenger seat were very bad. A couple fell apart taking the tape off.
Now for the bad news, fuse #2 still blows :P. The work was not for naught though as it did clear up another issue that I assumed was related to the body fuse issue, but apparently was not.
That said, I'm going to cut that splice 311 back apart and troubleshoot from there. It was one of my first splices and I'm not real happy with the soldering job on it so I was kind of wanting to re-do it anyway. My technique got much better 3 or so splices in and from there I was real happy with them.
One lesson learned though. The wiring was pretty well tarnished. Even stripping the insulation back the wire underneath was black in most cases. One of my biggest struggles was getting the wire clean enough to take the solder. A little research online, I found a guy that works on boats (highly corrosive environment) that used muriatic acid to clean contacts. I tried it and it worked fantastic. My procedure was to dip just the tip of the stripped wire into a can with a small amount of the acid and let sit for 5 or so seconds. The wire comes out almost perfectly clean. Then dip into water with baking soda to neutralize any remaining acid, wipe dry with a paper towel and then wipe down with rubbing alcohol for a final clean. That saved my fingers from a lot of rubbing with sand paper, which is what I tried first and concluded "there has to be an easier way." Thank you Chemistry. EDIT: Here is the youtube video I found https://youtu.be/mMF5bhbucro?si=ip5vALkUCoUKHBRC
For those interested muriatic acid is Hydrochloric acid (HCl) and can be bought at home depot as a strong concrete etcher/cleaner. It is nasty stuff so you want to follow all the precautions on the bottle for sure. Baking soda works well as a neutralizing agent. HCl does not react with copper, but reacts strongly with copper oxide. It will cause copper to corrode faster because as it reacts with the copper oxide it continuously exposes fresh copper to oxidation, so it is important to get it all off the copper after the cleaning is done.