1. Time: in the screenshot it shows time from the beginning of the capture file. What actually is encoded in the capture file is the absolute time (in UTC) and it's indeed encoded in the Timestamp field.
2. Depending on the packet this is usually packet.Ethernet.IpV4.Source.
3. Depending on the packet this is usually packet.Ethernet.IpV4.Transport.SourcePort.
4. Depending on the packet this is usually packet.Ethernet.IpV4.Destination.
5. Depending on the packet this is usually packet.Ethernet.IpV4.Transport.DestinationPort.
6. Protocol isn't really encoded in the packet. It's more of interpretation of the Wireshark and usually doesn't contain all the information. It can usually be deducted by combining:
b. Assuming (a) is IP - packet.Ethernet.IpV4.Protocol
c. Assuming (b) is TCP or UDP - packet.Ethernet.IpV4.Transport.SourcePort and packet.Ethernet.IpV4.Transport.DestinationPort (usually the minimum of the two).
7. I'm not sure to what size are you referring. packet.Length will give you the total size of the packet in bytes.
8. Like Protocol, this is just a string that combines different values depending on the different protocols values.
I hope this helps,