ouR escaPOD mods

It shouldn't matter. The monitor reads a voltage across the shunt and interprets it as a current flow. Since it is clocking amphours in and out it would need to be disconnected for a considerable time to effect the capacity measurement.

A capacity monitor should be able to use the full charge battery voltage to reset itself to 100% SOC. Otherwise it would build up errors if you were say to cycle the battery between 50 and 80 percent for a long time. By using full charge voltage to reset occasionally it knows that that battery is at 100% SOC. Since Li batteries can have differing full charge voltages does your capacity monitor have a setting where you can adjust that?

A good battery capacity monitor has a bunch of other settings too. Here for example is Victron's monitor setup parameters.

Victron

I wasn't expecting it to. I'm sure there's nothing wrong with the monitor you have. Just pointing out what settings are used to get really precise SOC measurements. A less expensive monitor without all the settings won't be as precise. As I said before, your monitor is only about 5% off right now, that's actually pretty good.

You might find this an interesting read.

Lithium longevity

Yes, even if most of the information applied to Lithium Ion and not LiFePO4. Table 2 was the one that was of interest. I think that the larger battery and trying to keep it above 50% SoC would likely give me the best outcome. The trailer will be gone long before I would exceed the number of cycles indicated. 3000 cycles if it were taken to 50% every day would be over 8 years. Most likely, it would stay above that and give an even longer life.

Not at all surprised by the fridge energy consumption. The weather is starting to get hotter now. Front loaders are less well insulated than chest fridges, especially around the door seal. If you get into some really hot weather you will probably use close to that in 24 hours. The 200AH battery is a good choice, and you don't have to agonize if you need to cycle it more than 50 %.