On the homepage, I'd like to see what it looks like if I hid the main image and had the text spanning the page. Is there CSS that can make that happen.
You can hide the image with:
I'm not sure how to make the text span across that area, but you can ask for advice on that here:
how do I submit a site to be featured in the "Awesome blogs using Theme Name" section on each theme's info page?
There isn't any way to submit for that. The theme team selects sites from time to time.
Also, is there a way to customize the site's html title tag?
There isn't any way to customize the meta tag, but your Site Title is used as the title meta tag, so you can edit that to be whatever you like, and the tagline field is used as the description meta tag. Typically Google will show your tagline/description in its results.
I hope this helps! :)