Removing the ampersand in '/opt/bootsync.sh' is not going to change things for you and you better put it back as it serves a certain purpose.
The two scripts are having different roles: '/opt/bootsync.sh' gets called pretty much at the very end of '/etc/init.d/tc-config' and should contain those user specific startup tasks that need to be completed before anything else gets on it's way. It itself then calls '/opt/bootlocal.sh' (as a background process due to the ampersand) which should contain those user specific startup tasks that can run in parallel with other processes. In summary: '/opt/bootsync.sh' is used for synchronous tasks and '/opt/bootlocal.sh' for asynchronous ones.
I'd bet your problem is that your USB stick is not recognized early enough in the boot process to contain the backup file, and therefore nothing gets restored which means your your changes to any '/opt/boot*.sh' files are having no impact. I'd encourage your to read the relevant part of the
FAQ and adjust your boot loader configuration to contain the appropriate 'tce=...' and 'waitusb=...' boot codes.
BTW, you can check whether your USB stick's 'tce' directory is being recognized via
cat /opt/.tce_dir, where a value of '/tmp/tce' would be a prove of my assumption.