I am on Win 7 and Firefox right now. The keyboard down arrow moves the page one line per key press. Hold the key down and it scrolls down the page. The scroll bar on the screen does the same thing - one mouse click one line, hold the mouse button down and it scrolls down line after line. I never set anything special but Win 7 has very customizable mouse features. Just open the mouse menu in the Control Panel and adjust it to move pages any way that you want it to.
As to clicking an X to close a webpage - just set Firefox to open a new webpage when you enter a new URL in the current tab. It will just go and open a new webpage and the old one is gone. FF keeps playing with their tab feature which is a pain in the a - if you want more than one webpage available on different tabs you can set to do that too.