How to remove html widgets on the sidebar and make full-width blog posts after clicking the 'Read More' button on Blogger?

My blog looks like this: Sidebar on the Left, Blog Post on the Right.

My Sidebar on the Left is made up of a series of HTML widgets, like an About Me Widget, Twitter Widget, etc.

My Blog Posts on the right all end with the first sentence—then there's a 'Read More' button!

This is what I want to do: I want to be able to click the 'Read More' button and be taken to a page where my blog post is full screen. This thus means removing all the html widgets in the sidebar.

I understand that to remove the HTML widgets on the Left Sidebar so they only appear at the Home page requires some <b:if cond> coding. I already know how to remove the HTML widgets on the Left Sidebar with it, so that they only appear on the Home page. However, my blog posts are not full-width after clicking 'Read More'—instead of reverting to full screen size, they remain the same size, with a gaping vertical blankness where the Left Sidebar used to be.

Does anyone know what codes can be used to remedy this?

Please help! Thank you!