Moving imported tumblr posts off the index page

My website is https://www.kateasdfjwai.com [remove the “asdfj”]. I’m using the Scribe theme from OkayThemes.

When I imported my old tumblr posts, I mistakenly opted to have the posts start on my index page. Is there was a way to shift the posts onto another URL, so that they start on (for example) https://www.kateasdfjwai.com/tumblr and continue on https://www.kateasdfjwai.com/tumblr/page/2 …etc? Essentially, I’d like to have two blogs simultaneously… one that I’m updating on the index page, and the imported tumblr one at a separate link (that I’m still debating whether to keep/share).

I was wondering if this is possible, as I’m aware of the distinction between Pages and posts. Would the recommendation then be to keep the index page as a landing page, from which to direct people to ~/blog and ~/tumblr?

A second question: why are my tumblr-imported images appearing on the blog as thumbnail-sized, and how can I fix this? (My theme does not offer support.)

Thank you for your help!