WIGuide

The pro's you're seeing running all day on their batteries are using bigger batteries. Group 24 series are about the smallest used for a trolling motor and you'd see those on something like a jon boat. The group size is the physical size of the battery and most bass boats would be running a minimum of 27 series and many run group 31's. I would think they'd run a little longer, but maybe not. Since you're in La Crosse, go to Team Marine. The guy that owns it is a good guy and will get you back on the water where you can actually fish a full day. If it's a battery issue, Interstate batteries are sold all over here and they should be able to warranty them if needed. You might have to buy a couple batteries, but it would really be terrible to come all this way and not even be able to put a full day on the water in the National Championship. 

Both C-Map (Lowrance's mapping brand) and Navionics (Garmin's mapping brand) allow you to preview their maps on their websites. The only C-Map card compatible with your unit is the Discover map card which covers the majority of North America. To preview what the maps look like, go to https://www.c-map.com/chartexplorer/ and be sure to select the Discover/Reveal option and leave the toggle off for shaded sea floor as that's only available on the Reveal card. 

If you're looking at Navionics, only Navionics+ is compatible with your unit. https://www.navionics.com/media/wysiwyg/docs/Compatibility_Guides/GPS_Plotter_Cards_Compatibility_Guide.pdf This will show you what features will work on your unit and going here https://webapp.navionics.com/#boating@6&key=sfrrGjkmfP will allow you to look at their maps as well as the "sonar charts" aka user gathered and uploaded data to help build better mapping. 

To my knowledge Lowrance doesn't have a y cable to split a transducer to two units. Networking them together allows the information to be shared between units. When it comes to compatible units, you'll want to look at a Carbon, Live, Elite FS, or a Pro. All of them allow for ethernet networking which is as simple as a single cable and will share waypoints, charts, and sonar data. The FS units only have one ethernet port where the HDS 9 and above units have two, allowing you to add more of them to your network. You can network older units as well, but usually that will put the newer units on the network into legacy mode to be compatible and limits their ability. If you wanted to use your older unit exclusively for a chart and just want it to be able to share waypoints, you can set up a NMEA2000 network. It would be slightly more expensive and complex, but since it doesn't share sonar or map data, but should prevent your Live unit from entering legacy mode. 

I've got a Drotto and I really like it. In all honesty reaching under and clipping it was never that big of a deal to me, but depending on the landing, sometimes walking up to the font of the boat would make it slide back a little and then you're getting out to crank it back up tight. With the Drotto, drive it up until it clips and get out of the boat, or have your partner pull you out. Living where I do, I see a ton of different landing in a year, some so shallow and flat you have to take your shoes off to get out of the vehicle if launching solo to others that feel like you're backing off a cliff. I haven't run into a situation yet where it didn't work. I highly recommend. 

The little grey box is an auto reset circuit breaker. The red caps look like something they found to cover up the terminals. 

I fish them pretty much the same. The only real difference for me is I'll slow it down a little more when I'm fishing largemouth with them as largemouth get more lethargic quicker where a smallmouth will stay a little more active in cooler water than the largemouth will. I might throw something a little brighter for smallmouth, but usually the cold water periods have the clearest water of the year so natural colors aren't a bad choice regardless of species. 

Not sure what kind of boat you have to know if this would be a cheaper alternative, but Ashmore Marine Products has a "helping hand" device that tightens down with your locator gimble and can hold your rope up higher. It doesn't provide a post for you, but would keep it higher so you wouldn't have to bend down as far and doesn't take away from your deck space. 
https://ashmoremarine.com/shop/ols/products/xn-helpin-hand-ti3f

All you have to do is skip taping on the upper stationary shaft. I have a Ghost instead of a Fortrex, but the shaft concept is the same as the cable steer motors or any with a stationary head design. The trolling motor will only raise to the point where the bottom of the upper shaft is at the bottom of the mount. The FF transducer mounts to the lower shaft so secure the transducer cable to the bottom shaft and if you do tape it to the stationary shaft do it right at the bottom and be sure to leave a small loop of slack at the top which allows for the lower shaft to rotate and not put pressure on the wire and then either tape the wire right under the trolling motor head, or straight to the cables.
As far as adjustment, the Fortrex has a collar with a thumb screw to adjust height just like the Maxxum. 
 

If I was taking my best guess, there's probably a bit of ice left in the bottom of the boat. Those plugs have a piece of plastic that extends into the hull so when they are unscrewed they can just hang there and you won't lose it. If there's water left in the hull and it froze, it probably froze around the plastic in the hull so that would explain why it twists a little but not keep coming out like it's supposed to. 

You do realize this is Wisconsin right? I'm pretty sure the only fish being that big that you're going to pull out there would be of a different species.

Try them both, one might work better one day the other might work better on another. Depending on water temps, this time of year might be really good lizard weather if the bass are moving up to spawn or starting to. I believe salamanders can be egg snatchers so they hate them with a passion. 

If your cables are ok and there isn't enough resistance for you on your steering there is this option : http://www.trollperfect.com/Pages/default.aspx
I haven't used one but they get pretty good reviews.
 
The 6th speed is an off position. I know the older ones used to have a stop sign shape, where the newer ones had a symbol like the one you described.
 
Those big knobs control your break away tension. It's so if you hit something with your tm it will swing up and hopefully over it instead of just bending the shaft. Those brackets are slightly temperamental given that it doesn't take much of a turn from the break away to go from loose to pretty tight. You don't want it set too loose otherwise your TM will be swinging in and out Try to set it up so it takes about the same pressure to make the tm break away as the power that it puts out. That way when you do hit something you can turn your tm on high, point it in the opposite direction that it folds under, kick it on high, and it'll return to normal running position. (hopefully that made sense)