Header size issues / dynamic scroll / column width

I’ve got the 5 Hacks for Twenty Seventeen theme https://premium.wpmudev.org/blog/five-hacks-twenty-seventeen/#github, but have a few questions.

My site: http://www.reintention.com

1. I can’t change the header size on this theme or Twenty Seventeen. When I remove the logo it resizes to even smaller. How can I change it back to the original 2000 x 1200px or a custom size (ie. 1000 x 600 px)?

2. I can’t change the two column setting to 1 column, I don’t have the theme options tab on the customiser? I’ve tried changing the static page to “you’re latest posts” and this doesn’t work. I’ve also tried deactivating plugins and haven’t seen any difference

3. How do I create a dynamic scroll like on these examples (1) and (2)

4. I’ve downloaded the Advanced Twenty Seventeen plugin and I can’t change the custom footer, even when I change it it still appears as “Proudly supported by WordPress”.