Hello,
If you offload cron job tasks away from user requests, this will make a difference in frontend performance, but only if your site has enough traffic.
Unfortunately I do not have numbers for you in terms of matching number of users or requests to server capacity.
About your other question, it seems that the cron nonce has changed. This would happen if you uninstalled and re-installed the plugin. Simply use the new cron nonce in your curl command.
with regards