Need help adjusting post text width and number of lines shown (Photolux theme)

I’m a total newbie and am trying to figure out why my posts run off the page on my blog, The View From 30,000 Feet. I really need to correct this aspect of the posts and, secondarily, would like to figure out how to show the whole post rather than just the first few lines and an ellipsis that forces readers to click through to read the rest.

I would really appreciate some help with as much plain English as possible! Thank you in advance!!