Node suddenly failing

yes you are correct.

there are none. But the usage depends on customers, so the more amount your node have used, the more deletions would happen. So at some point they would become almost equal. I do not know what’s the current equilibrium point.
Our documentation suggesting to provide 24TB per node as a maximum recommended size, however it’s not a requirement, it’s a suggestion.

We do not provide such advises. We always recommend to use what you have now and what will be online anyway, with Storj or without. In that case all income is a pure profit.
You may use this Community Earnings Estimator to get an idea how long it may take to fill all the provided free space and how much you may earn:

The node will be disqualified by each satellite independently and the held amount on the satellite will be used to recover missing data on other nodes:

If your node would be disqualified not on all satellites (you were able to recover almost all data), you may continue to run the node, all other satellites will still pay for the usage. If the node is disqualified on all satellites, you need to start over: delete the current identity, generate a new one, sign it with a new authorization token and start with a clean storage.