-Don't get distracted by red herrings. In Most cases, frequency of lowest swr is very close to frequency of resonance. The difference is seldom significant when dealing with sufficiently broad-banded antennas like dipoles.
-The insulated wire, and temporary wrap over can be another confounding factor. Use insulated or strip the working ends, or let it hang down, whatever. Pick a method and stay with it.
Once you are satisfied with the pruning, leave it alone.
There is no reason the wire must be stripped and soldered. Just secure it mechanically so it is secure, e.g. wire ties, tape, dental floss...
-Make no mistake, attic antennas are greatly affected by the house and all the stuff in it.
-This is one dipole you absolutely should use a quality 1:1 current balun!
-A nearly flat swr across a band is a clue of possible problems or misleading/misinterpreted readings (you must understand the factors). Get up in the attic with about 10' of coax and make your readings there. Expand your readings outside the band until you start to see some sort of obvious dip/bowl shape!!! Plot out your readings for a visual presentation, even if roughly on a cocktail napkin.
-No dipole free of confounding influences (or really inefficient design, ala Bazooka) will ever give you a flat swr across the 10m band. It is just too wide. Same for 40m-160m. The narrower bands, can usually be covered with a single antenna, but you should still be able to see a definite curve if you expand your measurement frequencies. This is your cross check!
-Fan dipoles can be very touchy to tune. Wider spacing helps (most people probably use about 6 inches, but actually "fanning" them out helps more. They interact. I suggest starting with the longest element working to shortest, since the longest element will be less affected by than the shorter elements. Several iterations will be required.
-I don't trust the "flat 2:1 swr" readings until you take wider readings. Once you do confirm you are pretty well centered at the lowest swr within the band, realize that
*Given the antenna design, the location and height, you may not do any better than 2:1. This isn't bad. You need a tuner. Even with the best pruning it is not always possible or reasonable to expect a perfect 1:1 swr on any given antenna!
Keep pluggin, there is lots of learning going on! Bill