[Twenty Thirteen] Widgets Overlap and Comment area size

I am very sorry if this has been asked before, my search-fu is still quite green.

For the most part, Twenty Thirteen works great, I managed to fix most issues myself using custom CSS but this one has me at my wit’s end.

Due to the post size, the widgets just roll over the comments, as you can see here: https://papogp.com/2009/04/01/pmbok-4%C2%AA-edicao-download-gratuito/

I also have a secondary issue: I enabled the Paginated Comments plugin and it messed up the comments making them stretch over the whole screen area.

I’m open to suggestions (since I have no idea what can possibly fix this). Thanks in advance!