Help setting up Ledger Nano S & alt coins

Ok so I have the Nano S already setup and just have a few questions.

First of all, when using MyEtherWallet.com to access my Nano S, when I'm viewing a particular ETH wallet under "View Wallet Info" I see the public address, but do not see any private key.

Is this how every single wallet stored on my Nano S will be, with no private key showing/needed because the Nano S ITSELF is the private key for all of these wallets it would store on it?

Will that continue to be the case for newly created MEW or other various alt wallets, or just the ones that were installed on the Nano S by default and any newly created MEW or the like will actually have a visible private key?

From what I understand, you can pretty much add any ERC-20 token to the Nano S, you just have to manually enter all of the ERC-20 token info into a newly created MEW from a website like ethplorer.io - is that correct?

Are all of the ETH wallets pre-installed on the Nano ERC-20 compliant, or MUST a ERC-20 wallet be created through MyEtherWallet.com and then added onto the Nano?

I see all of the various Nano Ledger approved alt coin apps through the google chrome app, but this is still a very small list.

So how do I cold store all of the other alt coins that aren't on Ledger's list, are past the ERC-20 token ICO stage and have their own legit coins now? Do I just have to leave all of those on the exchanges? This step worries me as most of my holdings are everything other than what Ledger has already approved lol

I know for whatever reason the Nano S only allows 4 apps installed at one time, I assume this has to do with the onboard memory these things have. Why didn't they just make them a little more capacity, memory is so cheap there's really no excuse for it, especially for a $100+ item in this day & age.

So once you add one coin onto the Nano S through an app & then the Nano S updates the blockchain showing it holds X coins in one of it's onboard wallets, you can then remove the app and add another coin and everything is safe because it has been updated on the blockchain and the Nano S is actually the PRIVATE key to access the public wallet stored onto the blockchain with your coins? Is all of that correct? Or is the public key & therefore your coins also physically stored on the Nano S?

Do I need to close out of the Nano like I do a normal USB drive to make sure I don't corrupt any data?