It sounds to me like your performance issues may be related to jvm arguments, you said you fiddled with them, but what are you using? I use Eyamaz's jvm args tweaked for my particular memory situation and my minecraft works great. To get vanilla minecraft to work with java 7 either uninstall java 6 or use the profile editor to point the profile to the correct java location (Java Settings 'Executable') (/Library/Java/JavaVirtualMachines/jdk1.7.0_40.jdk/Contents/Home/bin/java on my system). I have noticed some graphical glitches in 1.5.2 when starting up with the new lwjgl, but these only appear at startup and the game otherwise runs smoothly. Go here to get instructions one what to do with those files (pay particular attention to the part about copying and renaming one of the files). You do mention extra files, and that's because when you download lwjgl it gives you all the files you will need for every operating system lwjgl works on. It sounds like you have at least attempted this. You will need to update lwjgl manually for ftb since it uses Minecraft 1.5.2 and earlier, which ship with the old lwjgl. You cover a couple different issues here so I'll break it down. I'll start off with saying that I am using OSX 10.8.5 and java 7u40 with minecraft, and it's working quite nicely. Hope someone who knows what they are doing chimes in before I tear out what is left of my hair. Look for more detailed documentation on the LWJGL site.

With FTB, I no longer get all the 'system can't keep up' flags in the console log, but it only takes a few minutes for the control & graphics responsiveness to start feeling mushy & sluggish. Vanilla minecraft (1.6.x) insists it needs Java SE 6, & I have to use the terminal app to get it to launch with Java 7. I have at least swapped out the LWJGL files that minecraft & FTB ship with, but there are extra files that came with the update & I'm not sure if I should install them somewhere. I finally broke down & updated my OS from 10.6.4 to 10.8.5 so I could install Java 7, only to find that minecraft doesn't like Java 7 on the mac & I'd have to update LWJGL to get it to run at all. Does anyone know how to properly put these things together & make them play nice with the current Minecraft & FTB launchers?

Minecraft java se 6 runtime