That's why I used quotes. The concern expressed was around excessive hydraulic compliance (softness) in the brake system, thus resulting in greater master cylinder stroke to achieve a given pressure, be it via brake pedal stroke on a car or surge brake actuator stroke on a trailer. Sounds like...
If you're not feeling excessive motion on the surge coupler after bleeding, I wouldn't worry about the brake lines. They may introduce more of a "soft pedal", but if it feels fine while towing and the brakes engage, I wouldn't replace the lines unless another reason comes up.
Don't top up thru the dipstick hole. With the drive level, once oil starts flowing from the overflow hole, stop filling and you're good. You only need to be anywhere within the indent on the dipstick.
The challenge with an insert is getting the a good seal with the O-ring. Oh, and keeping metal debris from entering the drive... I'd just get a new cap.
The cable housing needs to be in the slot. I would confirm that, then adjust as best you can and see how it shifts. Maybe the cable is stretched. If it doesn't shift well, then I'd replace the cable assembly.
The cans are mini-terminal blocks that attach to the positive terminal. The black rubber items are fuses. If it were me, I would replace those attached terminal blocks with a separate covered power bus bar mounted nearby. Mount all the excess positive wires to the bus bar. Check Blue Sea for...
You should have sufficient access to the water inlet to replace it if you trim the drive all the way up, as shown in the video below. Otherwise just pull the drive off. You don't need to separate the upper housing to replace it.
