Thanks for posting. We're a bit limited in our support of adding custom CSS code to the plugin sign up form, but I'd be happy to offer some help to get you started in the right direction.
Ultimately, in order to have the subscribe button display like the "search" button on your site, you'll need to apply the appropriate CSS code that your WordPress theme is using to create that button design. To do that, you'll need to first identify what CSS code is doing that. The best way of doing that is by using something like Firebug or the inspect element tool on your Chrome browser to view what CSS code is being applied to what elements. In using this, you can see what CSS code is being applied on your "search" button, so that you can apply that onto your Subscribe button. I'm afraid that the process of identifying and applying that CSS code is something that would have to be done independently, and we would not be able to help in that regard unfortunately.
For your latter request, making the subscribe button display a "hover" finger (I believe you're looking for the CSS "pointer" finger), can be done by adding a small bit of CSS code to your WordPress theme's stylesheet:
This targets the plugin's sign up form's subscribe button and should display that pointer finger that you're looking for.
Let me know if you have questions!