Please let me know if you have any luck. Its probably something simple to do with Bludits permisisons/links but I know nothing about PHP scripting and nginx knowledge is limited. You might have more luck following this link specific to Debian unstead of ubuntu.
I think issue may be something to do with this line:
Change the ownership of the /var/www/bludit directory to {your_user}:
sudo chown -R {your_user}:{your_user} /var/www/bludit
I’m not sure what to put in place of your_user and obviously /var/www/bludit needs to be var/www/mywebapp but perhaps budit php scripts expects this directory to be bludit not mywebapp so fails? Not sure.