I’ll look into this further.
To answer your first question, yes you want to use ‘unconventional server’. “unconventional server” is just another way to say "doesn’t use server.properties".
The MineOS webui does not deal with firewalls; this helps keep it distro-agnostic. So, any port you choose in MineOS for Pocketmine will immediately be working; Ubuntu by default doesn’t enable any firewall rules, so that shouldn’t be an issue.
No, for the last issue, “download failed”, I’m not sure why this happened. I’ve been able to download this profile successfully in the past and it hasn’t changed in the codebase recently, so I’ll look deeper. With the error happening where it did (on the extraction part), it is not likely anything related to php or libraries missing–it hasn’t yet gotten to that part at all by then.