Painfull

Does the server have the same ID's for the Adv. Machines as the Clients? Otherwise it might be a Code bug. I'm not sure, I'll look into it after the weekend.

Last thing I can suggest to help with the problem is maybe changing it to a Red Power 2 based system with Sortingmachines and Pneumatic Tubeing. Maybe the SMP code of BC (Maybe even SSP) pipes isn't up to scratch to sort that much info at once. I can remember a Plugin which would let you see what was Ticking a lot on your server but can't remember the name at the moment. Will look it up in the near future.

Forge tries to make all the id's work with conflicts it randomly assign's new ID's to the items, that's why the item ID differ.

Go into your Tekkit folder, and find the corresponding .cfg's in the config folder.

Also try to stop all the items in the pipes by stop putting stuff in them, maybe that will stop the lag a bit. It looks like you have A LOT of stuff running through them, and that can't be a good thing.

Try getting optifine out of the mod, some people it just doesnt work for.

Item ID 240 is used by Resin from IC2 and something from Red power 2 wants to use it. Change the ID.

NullPointerException in my experience happen when the server has a different ID for the items you are trying to craft then what the client has. Check that your ID's match.

What IP are you giving them, also can they ping you?

Go into your Tekkit folder (found in Windows %appdata%/.techniclauncher/tekkit/) then go into the config folder. It's either Enderchest on ID 177 or Alchemical Chest on ID 177 change that to a unused ID (I think 122 is free) and try again.

Post the error log, or we can't help.

Without seeing the storage system, where there might be a few conflicting ticks which make it slower. I can't help any further.

IP = 10.0.1.8 is a private adress, try getting your public address at http://whatismyipaddress.com/ and seeing if your friends can connect to that.

A fast google search gave back that you might not have the right permissions on your OS to make it work.

It might be optifine. Try getting that out of the .jar file.

That happens on server if you're Item ID's aren't the same as the servers. And you have a item with a ID conflict.

Crystal chests show the items inside the chests, somehow I think that 240 chests are a bit too much for your/any PC to handle. Try it with diamond chests.

You probably didn't delete all the mods that are dependent on Buildcraft. Things like AdditionalPipes.

If you want to make it a public server you need to google "How do i forward ports".

ID 177 is being used by Enderchest (I think) And Red power 2 wants the same ID. Solution change Whats on ID 177 to an unoccupied ID.