To tighten up the spacing at the bottom of the Chateau theme, start by adding this to your Appearance → Custom Design → CSS editor:
.content #content,
#main .full-width .post-entry {
padding-bottom: 0;
}
.post-content {
margin-bottom: 0;
}
Adjust the numbers to add back spacing as necessary. Note that there is placeholder spacing for some things there which aren't currently showing up, such as comments, so if you add comments or things like that then you may need to adjust the CSS. Also note that the Edit link takes up space but it's only seen by you and not by your visitors. Try testing on a few different types of pages to see what works best for you.