You say it shows up in Disk Utility, but doesn't mount? What does Terminal say is the Device Identifier in Terminal? The command to check is "diskutil list" (without the quotes). It'll then list all drives connected to the computer and their partitions. It'll have your primary drive as well, so keep an eye on the drive's name. It should be something like /dev/disk0 and the partitions will be sequencially identified as disk0s1, disks2, etc. You're wanting the /dev/disk# info for the Passport Ultra. Once you get that info I can tell you how to copy a drive/volume/partition without it being mounted by the system. But it'll take some Terminal work if you're comfortable with it
If I'm understanding you correctly, The joy con is connecting physically, but the switch isn't recognizing that it's connected? https://en-americas-support.nintendo.com/app/answers/detail/...-con-not-recognized-or-not-registering-while-attached-to-the-console Nintendo recommends making sure your system has all updates to fix any firmware issues. Then, try power cycling the switch, detach the joy con, reset the joy-con’s connection by pressing the Sync button and then a button on the controller. You should be able to attach it and the Switch recognize it. If it continues to happen, just the right joy-con would have to go in for servicing. The above link has the info for Nintendo repair services if you need it.
Unless you happen to have a backup on an external sd card that you saved as a .zip, you'll have to take it in. If you can, try to boot into recovery mode: power it off, hold volume down & power until the LG Logo pops up, release and repress the power/volume down, then hold until the Hard reset menu displays. Click Power to select Hard Reset and it should enter recovery mode where you can install update.zip from an external sd card, recover from a backup, or erase everything and start over)
So the motherboard you have can take up to 16 GB total 1333 MHz, 1600MHz Ddr3 sdram. If you upgrade the Kingston 2x4gb with the hyperX fury 2x8gb 1600 MHz ddr3, that will still function with your board.