Addressing some of these items just in case someone happens across this…
The initial issue with the default style is that, not accounting for margins and padding, the width of the forms is 630px fitting into an area designated as 620px. That will cause a wrap.
You were on the right track looking at the post on customizing the stylesheet. You do NOT want to edit the file in the plugin editor (the one you did find) – any changes there will be overwritten when you upgrade the plugin.
The process the article recommends is to use one of the included stylesheets as a starting point and copy it to your theme folder. If you didn’t find it in your theme editor, it is likely you skipped the step of copying the file there. The reason this is recommended is so that you keep your customizations outside the plugin folder so you don’t overwrite them when the plugin is upgraded (assuming that you are also working in a child theme for the same reason) yet you can still edit it via an editor in the admin.
However, there is one last possibility, and that is using no styles. As of posting this answer, that is actually what you have. Whatever you specified for loading the stylesheet is not loading, so what you are seeing is not the 2011 stylesheet, but actually is no styles applied (which can be a good place to start from).