[TekkitClassic - Plugin and Patch Stop shop!]

Wow... that's all I have to say. :\

[Getting Cauldron with Tekkit difficulties...]

Your server provider must have a config file somewhere. The jar file might have to be renamed to a certain namespace that the config file requests. For example on my McMyAdmin config file on our server I also run cauldron, but I have to rename the cauldron jar file to spigot.jar to get it to work, that's just how McMyAdmin is currently working at the moment. Your server provider probably has something similar.

[I updated my modpack and now I get a 'Rendering global instance' freeze]

The pastebin log is not exhaustive enough unfortunately, not enough information. Look for your fml-client-latest.log in the log folder. Then paste that into a new pastebin, if it's too large then upload the log into a Dropbox folder and share the link.

[Looking for team to work on a fantasy Modpack for a server]

Hey there! Do you have a link to the mudpack or name? Curious to see the mods going into it. I'm a server admin at ubercraft.cap-minecraft.net, I was actually going to be posting a similar post.