There has been a few threads about No network connectivity whilst SIM card is inserted and a few solutions have popped up though not all of them are guaranteed to work. I would suggest you to first search through the forums and follow through.

Poor battery life could be caused by numerous problems. Again there are loads of threads that you can read up on and follow through to try and alleviate poor battery life.

USB port faulty could be a hardware issue (notably with the device). If your device is still under warranty I would quickly get your device fixed by nokia care before your warranty runs out. Also if you are still under warranty, make sure you read the fine prints that they may state. For instance, lots of numerous N900 owners have had their device replaced by an equivalent type which is not a N900. Again there's a bunch of threads about this and about USB connectivity issues.