Sorry for the late response.
Yes, Open() creates a PacketCommunicator that you need to dispose when finish with it.
Yes, you can create more than one PacketCommunicator on the same Device.
The different PacketDeviceOpenAttributes are documented.
NoCaptureLocal does make the communicator not capture its own generated packets, but in a lot of cases you filter that anyways so there's no need to specify it.
Promiscuous mode means that the communicator will try to capture packets that aren't aimed to that device (most simple Ethernet device drivers support this, with Wifi devices this is more complicated).
You can read more about these flags here:
I've added more detailed description in the code and it will be available in the next version of Pcap.Net.