I have two laptops with 1703 and on one of them only once had updates initially fail, but they succeeded second time around, although I don't bother with the apps store and don't have a MS account.
Quite often it can be down to MS servers.
However, as a repair install didn't fix the problem then perhaps it's something specific to your machine.
3rd party antivirus programs are a good place to start as they have been known to block updates.
Also, have you tried the updates in a clean boot should it be something else that is installed on your computer ?
Do you have any non-essential peripherals attached to you computer ?
I don't use Powershell and have restored the Command Prompt to the Start menu that the CU changes.
You can do that by going Start - Settings - Personalization - Taskbar and toggle it off.
It's unlikely that these cmds will work if a repair install didn't, but you can give them a try if none of the above apply.
dism /online /cleanup-image /startcomponentcleanup
dism /online /cleanup-image /restorehealth
sfc /scannow
You could create a system image onto external media and download the Windows Repair program at
www.tweaking.com and see if the app/store repairs resolve.
If you normally use Windows own system image, you'll find that the CU has removed the Control Panel from the Start Menu.
To have easy access to it, go Start - type control panel - right click on it and select Pin to Taskbar.
You may also want to check if System Protection has been turned off after updating to the CU.
EDIT - I've just learned that MS have released another update which takes the version from 15063.296 to .332 and while the fixes don't mention anything about updates, the MCT may have been updated to include this new release which may resolve your problems.
Hit the Update now button to see if yours gets updated -
https://www.microsoft.com/en-gb/software-download/windows10