You would need to create styles that override the SL styles in the
head of your page. Use the Safari Developer Tools to inspect the
overlay while it’s open. Control click on the border, and see what
element is creating it, then create a CSS style that has the same
selector which turns the border off.
No, not the way it’s written. Images which are larger than the
browser window are auto-scaled down to fit the screen, and unless you
are loading a foreign site (which forces SL to use an iframe) there
should not be any scrolling involved.
You can’t, really, because the scrollbars are only there if there’s
an iframe, and those are not styleable in the normal browsers, only in