Mars has no single permanent address and no clearnet site. It publishes several onion addresses, all resolving to the same market. Copy a current one from this page and verify it against the header.
It publishes more live onions at once than most markets, so a flood on one address never takes the market down. You paste another from the signed list and keep going.
Monero by default for privacy, Litecoin for small orders where Bitcoin fees are steep, and Bitcoin only when a vendor requires it.
Copy the address from this page and cross-check it against the address the page header prints and the login captcha. Never type a fifty-six character onion from memory.
No. A genuine login never asks for the recovery phrase. A page that does is a phishing clone.
Switch to another address here, Mars runs a deep pool. If all stall for several minutes, wait a short while, because floods pass.