hello!
[1] you best select a node for delegated harvesting
I’m not sure if i understand your question correctly but without selecting a node, you won’t be delegated harvesting. You must always select a node to start delegate harvesting. And if the node you selected shuts down, you will need to re-start delegated harvesting too.
[2] and if you get charged each time you select a node
You don’t get charged for changing Node. You only get charged one time, that’s for activating the delegated harvesting state of your NEM account. Changing node and Starting delegated harvesting is not the same, and is free.
[3] If a selection fails then do you get the nem activation back, or is that gone
Activation is valid until you send a deactivation transaction which costs 6 XEM.
[4] if you get any nem, when can you use it, Ie do you have to stop harvesting to use it?
Fees harvested are added to your account balance directly. You can spend them right a way. No need to stop anything.
[5] you go back to square 1 once you stop harvesting and reharvest
You will need to re-select a node or restart harvesting only if the node you selected goes offline or is not available anymore. (The icon in nanowallet will show a start icon again instead of showing the stop icon as when it is started.)
[6] how can you inspect to see which nodes have slots open
I don’t think you can do that from the NanoWallet but look in the forum for the NemNotifications Bot, if you opt in to this bot on telegram it will allow you to find harvestingSpace…
Another harvesting question is what happens to vested balance if wallet balance amount dips below vested balance requirments?
When you use some of your funds and your balance falls below 10k XEM, your vested balance will be adapted too. If your vested balance falls below 10k XEM you won’t be able to harvest anymore and you will have to wait until your vested balance reaches 10k XEM again (only possible when your balance is bigger than 10k XEM).
You don’t need to pay the 6 XEM fee again, your account is still activated, but is only not harvesting because you don’t meet the requirements anymore. Whenever you will meet the requirements, you will be able to hit the start icon button in the NanoWallet.
Cheers