The Suricata GUI package on pfSense is designed to make the deployment of an IDS/IPS somewhat simpler for users new to such technology. If you are at an advanced level where you want to integrate with multiple other systems and construct on-the-fly rules using script tools, then you really should abandon the GUI part of the package and simply use the Suricata binary itself. You can do that by simply installing Suricata from FreeBSD ports. You are going to have to install all of the other scripting language dependencies from there anyway. I am not in favor of loading up the Suricata package with a ton of new dependencies when the vast majority of users would likely not need them for a basic IDS/IPS. I'm talking about things like Python, Go, (and heaven forbid one old suggestion even needed Java! Can you imagine the security holes your firewall would have with Java installed on it?). There is a Github site for all of the pfSense packages here. You are free to submit pull requests there. I usally am asked for my opinion, but the pfSense developers have final say in what is accepted into the package.

@wafflez19 Go to the FLOW/STREAM tab and start increasing the TCP Stream Flow Memcap setting. The default is 32 MB (if I recall correctly), but with high core-count processors the default value may need doubling or even quadrupling in order for Suricata to start. The default value works fine on dual and quad-core processors, but higher core counts need much more Stream Memory. In your case, witih 16 cores, I would start with 256 MB and go up from there until Suricata starts reliably. Search this sub-forum for the same error (stream memcap) and you should find posts similar to yours with the solution. One of the posts in the past included the formula to use for calculating the amount of required memory based on your CPU core count.

Have you made a pass list yet?