If you have worked at large enterprises you should a few senior developers. Start talking to them. I'm a founder and I know a few other founders and that's how they all got started with the new startups/ideas.
No, the entire service is running in GCP as CloudRun.
If you have a public facing API with OpenAPI spec you can point and get a free assessment instantly.
I use CentOS on my personal server's largely because I use Red Hat at work, In past four years twice my servers were compromised coz I didn't applied security patches on time. Personally I like Ubuntu and I used it on my laptop for couple years until I switched to Mac, Installing patches, apps and upgrades are very simple on Ubuntu compared to CentOS, if you are a new bie I recommend Ubuntu.
I bet you will never attract the best, only those how are desperate will spend an hour with your tedious real bug solving interview. I'm pretty sure you are happy that this thing of yours is working out but let me tell you are not getting the best.
We implemented Shibboleth at Cisco after reviwing CAS and other products, remember it lacks Single Sign Out so you need to build this thing your self. You may also want to checkout OpenSSO which is open source and free folked from Oracle (Sun) Identify Manager
Focus is one of the most important leadership skill, we need to learn to take responsibility to finish our job, and have same level of focus for any task and its sub task's at all times.
If a child cries we can easily distract him by giving a new toy, but if we learn to keep focus on one goal I guess we can perform little better then the child.