1. What sort of network connection are you using? Wireless? Wired? Wireless connections can be quite laggy, depending on how good your signal quality is.
2. Why did making a dedicated server not function?
3. Have you added a lot of mods? Some weapons, such as mines or multi-shot/splitting weapons, can cause significant lag.
Last, for a dedicated server, increase DedicatedFPS in your config file to 10. I'd not recommend it above 10, unless you've got a nice fast LAN set up. 10 is good, generally. Basically, this is the number of frames updated to clients per second, syncing them with the server. Higher is less jerky, less laggy play, providing you have the bandwidth to support it. If you have it higher than your bandwidth can support, though, the lag will go way up.