Well, one thing I'd say I noticed from the first guy's crash report is that he's using the OpenJDK version of Java. The second guy, I'm not sure if Java HotSpot is one of Oracle's names for their reference VM implementation. If it's not the official Oracle one, replace it.
Despite being made by Oracle, OpenJDK most definitely is not the reference Java virtual machine and MineCraft can have some issues running with it. You should get the reference implementation of Java and run your server with that instead. If you use Ubuntu, you can find information to help you by going
here and scrolling down to the section labeled Oracle Java 7. For other versions of Linux, I'm sure a google search will provide an appropriate option for you. You're going to want to uninstall the other Java packages you had installed before installing Oracle Java 7.
If, after installing the proper version of the Java VirtualMachine, you're still having trouble, then it's time to get dirty.
First off, make a complete backup of your server folder, not just the world, but the entire server folder including configuration files and so on.. That way, if you make any mistakes or if I've given you terrible, idiotic suggestions, you can always start from the point where the server was only kinda messed up.
Now, with your backup made, let's start messing with stuff. It does seem to have ChickenChunks at its base, this would be the place I would start. I've never had an issue with this mod, but I have had issues like this with other mods. Generally, when something like this happens with a mod, it's for one of many reasons. Something has been placed improperly, an entity is loading improperly, or in some other way shape or form something attached to that mod is malfunctioning.
Fortunately, a nearly universal solution exists when this happens. Remove the offending mod from the server. It's usually as simple as removing the file from the server's /mods folder. In this case it's called ChickenChunks.jar. Put this file somewhere away from your mods folder. It's possible that more has to be done to unload the mod from your server, but I cannot seem to find any special information on it, so we've got this method to go off of. After you do this, start the server, crossing your fingers, and hopefully allowing it to start completely. If all looks well, then, you should then disable ChickenChunks from your client modpack temporarily through the FTB launcher, and then, attempt to login.
If you're able to connect and login, you're going to need to go on a tour. Enter creative mode if possible and fly around to as much of the world as you can quickly (walking/running/using jetpacks or gravichestplate or whatever if you can't do creative mode) making sure to visit any areas/regions/dimensions/etc that chunkloaders have been placed previously by you or users. This will ensure that the server registers that these blocks have been marked nonexistent and effectively deleted, thus allowing you to more or less go back to the beginning with that particular mod without having to completely reset your world.
There are situations where you want to save this option for the last choice, because in doing this, any block associated with the mod that's been temporarily disabled will disappear. That includes ores, trees, mobs, items, inventories, and so on.
After doing this, run the /stop command and allow the server to shutdown properly. If all goes well, you should then be able to reenable ChickenChunks by putting the file back in the server /mods folder and reenabling it in your client through the FTB launcher.
Before you start the server, however, you may want to mess with your ChickenChunks.cfg in your server's /config folder. I would recommend going into the file and editing it manually, taking steps to lower the number of chunks allowed to be loaded at a time. It's entirely possible that Chunkloaders can crash servers because they can make a server overextend itself beyond it hardware capabilities. If this was the cause before, this will help stop it from happening again. Also, set reload-dimensions to false for now at least. If your config file has signs of being corrupted (weird characters or something), then you can delete the file and it will regenerate the file at default values.
Now, if none of this helps, then you're going to want to look at BukkitForge. I'm unsure of how you'd proceed with that. It does appear both of you have Bukkitforge in common. I'm not familiar with BukkitForge, but it does appear that the version of BukkitForge listed doesn't match the MineCraft version number. Perhaps a place to start from? Maybe not, too. Either way, good luck. I hope I've helped.
