All along i thought it was the Billion, i was cursing and ranting about how crap it was, the poor thing. Well it still sucks for P2P as it gets flooded quite quickly but not as much as i thought it did.
Turns out the problem was with DDWRT. I tried out Tomato firmware and its now running perfectly with the modem in half-bridge, no disconnects, all ports forwarded and steady as a rock
Im not sure what the problem in DDWRT was an im too noob to figure it out. Ill stick with Tomato, easy to use and navigate, I had it up and running within 15 mins, including download, update firmware and configuration. So its all good for me and Tomato rocks!! Just wish they can add the Zune theme to it looks kinda bland thats only other comment ill make about it.