Lightning payment between two nodes
They payment is failing because you have opened a channel where node 1 has 10000 sat, and node 2 has 0 sat, and then you are trying to make node 2 pay node 1. 

From what I understand, in point 4 you are attempting to have node 2 ‘add funds’ to the channel you opened in step 3. This is not how a lightning channel works: a lightning channel is a bitcoin UTXO, and you cannot ‘add bitcoins’ to an already existing UTXO. Each channel is defined when it is created, and then resolved when closed (the appropriate balance is sent to each participant). 

Considering your setup, you can make a payment from node 1 to node 2. Once that is done, you’ll be able to make payments from node 2 back to node 1 (until the whole balance is pushed back to one side). 

What you could also do to achieve a similar result is opening a new channel from node 2 to node 1. I’m not familiar with c-lightning, but I know that LND let’s you open two channels with the same peer. As you mentioned, dual-funding is possible but has not yet been implemented.