Like any trading , its a risky business, even if you happen to know what your doing.
Crypto perhaps more so than other markets, due to many factors that make it a bit of a wild west - lack of regulation, the dominance of whales, manipulation, responsiveness to FUD, volatility, immature ecosystem.
Its very hard to time the market, so I don't trade much, but rather stick to your advice in point 8. I've done much better by opening long positions, and resisting the urge to sell out even when the market dips.
Yes, you are perfectly right. I have a hold XRP position with 80% of my portfolio. With the remaining 20% doing trading swing. More specifically: buy cheap and sell expensive, various coins. Minimum profit target: 100%. The time that a position remains open varies from a week to a few months.