Custom Image Size

In the section “The featured image of the post” of widget panel there is the option “Align the image to”. Have you tried “Left”?

Regarding the first question, I need to take a look at your site. Could you give me the URL?

Add this CSS rule in the Custom styles field:

.pis-thumbnail-img {
max-width: 150px;
height: auto;
margin-right: 10px;
}

Change 150 and 10 according to your needs.

Let me know.

Good choice in pasting those lines in your style.css.

Did you paste them at the end of the file?