1 BTC is not worth to hold in the long term, you need 50-100 BTC to get decent results.
That's is a good estimate, we will never know what would be the standard way of living in the future and things could go so expensive so it is better to have an excess estimate than a very conservative estimate.
Yeah 1 btc won't give you best returns and you cannot become rich with that amount, as price won't be in millions in future that even 1 btc can take care of you, better to have huge amount of coins.
yeah you are right 1 btc can give you only 50% profit in a long term investment the price is really high now and getting higher but there is not sure to bitcoin have a huge grow in price and take 1000% profit it is a little hard to bitcoin reaching 6000$ maybe in the future after 30 years or something.