Your vid cards actually has very little to do with java. The crashes you get aren't due to your graphics card, java is ram intensive, which eats up the processor like mad.
PermissionsEx is a plugin containing 3 plugins really. PermissionsEx, ChatManager, and Modifyworld. Permissions for ChatManager and Modifyworld need to be distributed or else they literally won't be able to do anything at all.
tekkit updates used to be as frequent as mc vanilla releases. Though the frequency is essentially irrelevant now because ForgeBukkit is dead.
http://www.mcportcentral.co.za/index.php?topic=3989.0 <-- proof
a lot of users do it by hacking with clients (i.e. the Crystal client) as for fixing this issue, I'm really not too sure, I haven't had many hack problems. with the combination of different plugins, you can set it up so that as soon as a player obtains a certain item that they're not supposed to have, they get automatically banned. Hope this helps and good luck!
I would suggest using a plugin called TekkitRestrict. with it, you can limit blocks to certain ranks, limit how many of whatever block a player/group can use, limit the charge on EE gear, disable mods completely, etc. It's a REALLY powerful plugin and I don't think I could ever run a Tekkit server without it.