You will have to leave 32 ETH in the network – this is the minimum entry threshold. You can’t disconnect it from Eth2 and Eth1 chains, the reason is establishing a stable connection with infrastructure.
What about the penalty system? What actions can lead to getting disconnected form the system?
You may be punished for violation of interests of the network – for long-term absence, wrong offers and attestation. That’s why you can’t disable validators for a long time manually. The platform can also reduce the reward rate significantly and disconnect you from network.
The last question is about safety. How are keys stored?
Every key is considered to be “hot”, meaning that the validator is active all the time and it uses the key to confirm the actions. The key is encrypted in a cloud storage because it’s less safe to do it based on the validator.