I agree with others that you should stop thinking about what more you need and find out how what you have works for you. True survival is often 2-3 days before you are found, so instead of having a multitude of blades, have a set amount of tasks written down, and test each knife for suitability in each area.
Because I am a knife guy I usually carry more than I need, but there is nothing wrong with that unless you are placing more faith in tools than on experience. I would suggest your bases are well covered with the Gerber (multi tool), the RAT (common use folder), the larger Fallkniven (heavier use fixed blade) and saw and chopper that you have. Once you get some dirt time with your knives you will understand YOUR strengths and weaknesses and may choose to fill those with your existing knives or branch out into new categories. If you are set on finding more knives before getting to work with them, add a $15 Cold Steel tomahawk or a CS/Tramontina/condor machete of similar value. That way you can evaluate what type of larger chopper works best with your style. Or a stockman/trapper/canoe slip joint.
When going out by myself I usually choose an axe, medium fixed blade, neck knife and slipjoint or clipped folder. But then again there is nothing wrong with buying more, just don't delude yourself into thinking that you NEED them to survive.
