I would tell him the money is in the mining of smaller coins. trying to trade high value things only really works if A) you know what you're doing or B) you can afford to miss until hitting it big with luck. at least if he mines smaller coins he should see SOME gains (not compared to cost of electricity and rig) but maybe it will at least lower the self destruction?

Bitcoin is a scam. Tell him to play with something safer, like Uranium.

One word: Tulip Bulbs Ok, that's two words, but you'll be so busy counting your profits from tulip bulb trading, you won't have time to count silly things like words.🌹

OP, hopefully you didn’t inherit your intelligence from your father. I hope you are able to support yourself some day, because Dad’s going to lose a lot of money before he figures out that he’s on a losing path - Or he runs out of credit. Instead of directly pointing out Dad’s folly try asking questions like what is he going to do if this doesn’t work out for him? Is Mom in on this too? She (or stepmom) might have more influence on Dad if they are still married.