Hi KT,

1. Thats up to your HTML and CSS. There are no layout layout limitations with SS.

2. Yep. Out of the box.

3. Widgets are your friend here I think. http://doc.silverstripe.org/widgets

4. Yep - http://doc.silverstripe.org/getcmsfields?s[]=content&s[]=area

5. There is a user forms module. http://silverstripe.org/user-forms-module/

Regarding the re-usable components: Usually a Widgets holds its own content. So if you have a Widget where you can enter some text, then this text will be unique for every Widget instance (i.e. not reusable).
But there's an easy workaround for this:
1) Create a custom DataObject that represents a content-component (could be composed of a Title, Text and an Image).
2) Manage your content-components at a central location (has_many content-components). The HomePage or SiteConfig is probably a good place for that. Use the DataObjectManager module for content-component CRUD. Here's a good tutorial that will help you getting started using SiteConfig: http://ssbits.com/2-4-working-with-siteconfig/
3) In the widget, simply allow the users to select the desired content-component from a dropdown (has_one content-component).

This will effectively allow your users to place the same content-component on multiple pages. Changing the component itself will change all "instances" of this component as well.

Actually for more than one content field, if you are lazy, there is a page elements module @ http://www.page-elements.com/