A few questions regarding ENS addresses

I want to register an ENS address but had a few questions. Hopefully some of you could help me out.

1. I can afford a 3 year registration fee for an 8 letter domain. Since my domain is 5 letters +, that means I'd have to pay around $5 every year after those first 3 I paid for? Are there any other fees I should keep in mind?
2. Can I pay for more years later on when I get more money?
3. I only store my Eth in a ledger hardware wallet (on mainnet) and use Metamask for developing on Ropsten. Should I (or can I) create a new address for this domain with my ledger hardware wallet, instead of using the main address where I keep all my eth? For the sake of privacy.
4. The registration fee is cheap, $24.79 USD for 5 years, but up to $120.32 USD in Gas fees? Is that for real?
5. I've never used Metamask outside of the testnet, so I'm nervous. I'm used to operating only hardware wallets. Any tips when registering my domain with my ledger?

Thank your much!