1) you must've set up that channel. Did you ask for a channel and have to pay a lightning invoice for the channel? Or did you open it yourself to someone? Best way to answer this question: do you have receiving capacity? Or spending capacity?
2) the sats you send to the node are there for you to open channels. Considering Alby hub needs to be online at all times, I recommend NOT using it for long term storage, but that's up to you. I think I have 9000 sats or something on mine because it's what was left over after opening a channel.
3) the node itself is an on-chain address and can't be used for lightning payments. You use the channels that are open to send/receive lightning payments. There's easier wallets out there to manage the on-chain payments than having to go back to your lightning node.