You shouldn't call it the "bo5" in FFA. Should instead say that we're "playing to 3 wins". It may happen even in 7 matches (2-2-2 -> some1 wins in game 7) so "best of 5" is misleading and inaccurate.
Yeah I think more points. You should multiply it by 1.5 (1.5 more points because there's 1.5 more players)