Do you still have Java 6 installed? Or do you not have Java 7 installed? Looks to me like it just stoped working. The terminal will give our errors and complaints, you cant do a thing about it. But it seems unusual for it to just stop. It set up the Ram, it loaded the proper set up Jars for minecraft. Everything is fine until it loads the minecraft.class. Ive never had this issue, (or mabie i have, i dont pay attemtion to the termial unless something stops working). Also, i say that you went into the "minecraft" directory, is that where your Launcher is? Because the Java fix command only works if the Jar is in the same directory as where you hit the command. Also looks like the Launcher doesn't have the correct permissions to go into the directory where all the minecraft stuff is stored. If you look it sais "Fixed Minecraft Path: Field was private static java.io.file..." Thats a red flag (to me) that something is private to external users and programs that shouldn't be. ALSO, i tried to launch the DireWolf20 pack and it didn't work. (the download didn't finish) but thats because I packaged the FTB launcher to to a .APP Application so i wouldn't have to take those painful steps.
If you would like to have the Launcher i made that automatically launches FTB, im sorry but i cant post it here. The admins would most likely take this post down or something ugly and i would get into trouble.