It is the Form Logo that is causing that behavior (the "City of SouthLake Texas" image). When you add a logo in the Form header like that, it automatically places padding on that side of the Form Title container, which also contains the pagination tabs, to accommodate space needed for the logo. You should be able to remove that padding on the right with the following CSS:

#form-title-wrap {padding-right: 0 !important}

Which should result in the pagination tabs spanning the full width of the page. Since the logo is so high up, you won't need that padding there.