Thank you for this feedback. There are some other posts in the Package forum where the advice for Nano users is to bump up the size of /tmp (and possibly /var) because the default partition sizes are too small to download and unzip the ever larger rules tarballs. Unfortunately, today there is no mechanism within the pfSense Package Manager system for a package to specify prerequisites that must be satisfied in order for the package to be eligible for installation. Some example parameters that would be useful are installed RAM and free disk space on critical partitions.
As a general statement, Snort or Suricata on a NanoBSD install will require a lot of careful attention and quite possibly some customizations such as you describe of increasing the default partition size for /tmp and also /var.
Bill