The battery cutoff switch is wearer proof, so it should be OK. I would have the dealer clean up the wiring issues, battery covers, and address the other issues, especially the underside battery jumper wire and shunt battery connection wire, they need to be at least No.4 AWG wire, go to the Victron Web site when you get home, and see the install videos they have for both the Battery Meter and the MPPT solar controller.
In this photo of your MPPT, I think I see the issue with the solar not working,
but can you send me a photo shot direct on the front, not at an angle showing where the wires are connected to the Blue solar controller box, tight space I know, but give it a go.
The larger aluminum tub is nice, and worth the investment, I am having one installed on my TaB also, replacing the original plastic one, which is gone anyway. You needed the extra space for the new batteries. Nice upgrade also. When our newish AGM quits, we are going to upgrade to lithium also.