I remember doing this once, but I'm fairly sure I did It through a live install. Make sure your target USB is properly formatted? I do remember that finding information on this was hard, because it isn't really a viable long-term option.
One thing to note is that you need to make some modifications to limit how often things get written to the drive, and even then you will probably kill your thumb drive pretty fast.
For your use it should be pretty safe then.
As for Creality, the couple of printers I've worked with from them are an absolute nightmare (but in their defense it looks like they were discontinued the moment they came out). I have the impression that the only positive comments you get about Creality printers are from people who haven't owned anything else, and joined this "tinkering" circlejerk. They're unpredictable at best and an electrical hazard at worst.
First of all, 30ft x 30ft sounds absolutely huge! Maybe you meant 30 square feet? If you're not printing non-stop and can open a window from time to time, PLA should technically be fine from what I've read, although a well ventilated room would always be best.
As for the printer itself, I personally would advocate against Creality products. I would trust a Prusa MK3S with my life, but it is on the pricier side. I've read good things about the Sovol SV06 (not the 7), which looks like an MK3S at 1/3rd of the price. Can't speak from experience though.
For your last point, you can add torrentio twice (in the order you want results to appear). One with only Real-debrid links, and one with "RD Download" links, for entries that have torrents available to torrentio, but haven't been cached. This will download the torrent to Real-debrid first, so it's definitely not as fast!
Not FOSS, but free and ad-free, from a small Japanese developer: Weawow. The only thing that requires you to make a small donation is to unlock a couple of weather providers, but you have a big selection without it.
I remember doing this once, but I'm fairly sure I did It through a live install. Make sure your target USB is properly formatted? I do remember that finding information on this was hard, because it isn't really a viable long-term option.
One thing to note is that you need to make some modifications to limit how often things get written to the drive, and even then you will probably kill your thumb drive pretty fast.