I'm in the process of downloading relatively large amounts of data from e621.net (I'm currently around 500MB in and plan to download 5gb+ if this post goes well) and would like to ask a few questions because I'm new to this website and their terms of service are a bit vague in my opinion.

Should I limit the download speed (to let's say, 100KB/s) to work as a failsafe to prevent going over that limit if e621dl is not limiting it's self?

Is e621dl more or less acknowledged by e621 to be an allowable means to download content from the site? I know that it shows up in the :Tools (link here) section but I'm new here and don't know if that's user-editable.

I just want to make sure that I'm not going against any guidelines and would like to stay on the right side of what the community/staff thinks. Thanks for your help.

Downloading them isn't any different than viewing them.
And there's already a limit on that speed.

It looks like the only thing listed as e621dl under the tools there is the one that I made, so I'll let you know that the script is open source. You can edit whatever you need in the source or the config. It also has a built in delay when making API requests so it should theoretically never go over the limit (which is one request every half second). The speed you download the image at has no effect on the limit, just how often the initial request is sent.