Please help me to understand lightning-cli getinfo more
First of all yes these are your earnings from routing. You can check lightning-cli listforwards to get a list (in json) to see through wich channel routings have been attempted and settled or failed. In particular you can analyze the routing fees per channel from the output of that command.

If you are interested in channel balances you can use lightning-cli listfunds to see how much balance is on which side of the channel.

As for the message you received someone offered you to balance their channels through you by asking how your capacity is organized on particular channels. You can find that information with the above mentioned listfunds command. You also have the power to share this information. Morally you should have the consent of your channel partners. 

As for python: Checkout my Hack a LAPP video series or my git repo for the code of that LAPP that shows how to interact with the Lightning rpc interface. 

most important lines will be: 

from lightning.lightning import LightningRpc
rpc_interface = LightningRpc("~/.lightning/lightning-rpc") 
print(rpc_interface.listforwards())
print(rpc_interface.listfunds()["channels"])


If you know python it should be easy to adapt to xls output