One of easiest way to create and access Ethereum and erc20 token is MEW web interface. My question is , is it safe to keep big amount in MEW or better not to rely on it.
No, it is not safe to keep the big amount in MEW. You better select the other wallets that support your coins. But if you still want to keep that tokens in MEW, you need to save your private keys or the other things you used to log in. If you can sell the token, it is better to do that before the price is down, so you can have ethereum in the other wallet, which will give you more profit than the token.