When looking at market cap and prices, I tend to look at the historical 24 hr volumes relative to the market cap. I feel this is a good indicator of not only open interest but also the utilization of the network.

I also share your nervousness given how far some of these assets have come. I like your risk management approach though. Consider using stop losses even trailing stop losses if they are available on the trading platform you use. This allows you to be more disciplined in your risk/reward approach. Only negative is that with the volatility and price swings, you can get stopped out pretty quick.