Players Timeout

[NoLiver92]

When I play my modpack (below) with friends on my server at home, I have allocated it 8Gb in the startup .bat file. But when I look in task manager java is only using 3Gb max, How can I get it to use the full amount? My system has 16Gb in it and is 64 bit with the latest java 8 64bit installed.

My Modpack: http://www.technicpack.net/modpack/total-craftania.647463

Also could be related, with 3 of us on the server we consistently lag and regularly time out which disconnects some players, I have mystcraft on it and one of my friends has his house in another dimension. It seems to lag whenever someone goes to another dimension or nether (ram maxed out at 3).

Can someone help me find the problem?