This is due to your CSS adding *padding* to some element inside the google popup window. You can clear padding off all elements with

.popupWindow *{
padding:0 !important;
}

Add this to your CSS

.found{display:none;}

Yes.  Using CSS, you can float your form elements left to right.  First, we float our form elements with

.locator_form {
border: 1px solid #EEE;
margin-bottom: 5px;
overflow: auto;
float: left;
}

Then ensure the form itself pushes the map down.

.com_locator_forms {
overflow: auto;
}

Now make sure the submit button is on its own line below the form elements.

.locator_submit {
clear: both;
float: left;
}

Use the h2.com_locator_title class.  For example, to change the marker title link to black text, use this CSS

h2.com_locator_title  a {
color:black !important; font-size:16px !important;
}

Use the .popupWindow class.  For example, to change the marker title link to black text, use this CSS

.popupWindow h2 a {
color:black !important;
}

To change all text in the window to black, use this CSS

.popupWindow * {
color:black !important;
}