I would make the sdcard with sdcardmaker using the uboot from the ROM you have, select full format not quick format option when formatting the sdcard.
Once you have the card made, copy all the files from the extracted ROM, including uboot.bin to the sdcard.
If all fails then I would try the command 'erase nand whole' to force it to read from the sdcard if it is not doing so already with your other methods

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