Regarding different outputs for the same seed: have You changed seed source to CPU in A1111? The noise You get that way is consistent across different hardware vendors and different from the GPU-sourced one.
I have used A1111 just now to check and got very simmilar results to ComfyUI that way.
My bad, I should have worded that better, thank you for making it clear, that's exactly what I had in mind.
General advice would be to look boring and hide your IP as much as you are able (get a domain). As long as you're not looking juicy you won't attract skilled attention. It's like locking a bike, most bad actors will just pass by looking around for one without a lock or a real fancy one worth their resources.
You can utilize Cloudflare's free offerings, starting with simple stuff. Their DNS Proxy is essentialy a single-click but will help substantially. You can build on top of that with simple WAF rules, such as droping connection attempts from IPs originating from countries notorious for "poking around". You can also reverse that rule and whitlelist only your country.
Keep your firewall tight, don't expose other ports, put your services behind a reverse proxy and redirect everything to HTTPS. Start simple, constantly improve, learn more advanced methods/concepts.
I used to run Authelia with NPM. It supports TOTP as second factor.
Pretty much vanilla, only --xformers --medvram arguments and CPU seed. In that case, someone with more A1111 experience should weigh in, mine is limited, I mainly use comfy nowadays and probably am not up-to-date with development.