That's a good one but not so great, I would've recommended MyBB, it's the best open source forum script which has NO LIMITATIONS and you can expand as much as you want plus it also has a ton of themes and there are many MyBB Devs./Designers out there including me
BTW, you use Discourse hosting?
Have you got DDoS protection?
Do you use CloudFlare CDN?
We aren't thinking of switching. And we love Discourse because it's less intimidating for new users. I've used many forum software (including myBB, which I don't like) and this is not bad at all.
I can't answer your questions, sorry. I don't oversee the technical side of things.