Have you tried this? Clear all tabs that you don't want, setting (and arranging--the left-most one is what will display when FF first opens) those that you do, and at Tools/Options/General/ click the Use Current Pages button. This should make the tabs appear the way that you prefer when opening Firefox.
BTW, I have a number of startup tabs, not just a homepage, and one is a blank tab so that I can open a website that I type into the destination window without overwriting the currently open tabs. I know I can open a blank tab with Control/T, but I do this so frequerntly it is a saving in time.
HTH |