I hear this line a lot, but it's not really true. Biden has immunity from criminal prosecution (which is obviously fucked up), but courts still can block his actions.
Unfortunately even your first bullet wouldn't work. It's not like these billionaires are walking around with their billions in cash. Most are held in stocks or assets, which would simply be inherited by whoever is set up in their will.
Given the partisan nature of the Supreme Court at the moment, anyone who thinks a Democrat trying to use these powers that they're saying the president has would get away with it is extremely optimistic at best.
That's why he could do things that are un-blockable. Like immediately adding 14 partisan judges to the SC. Then they are the majority that would determine the constitutionality of their own assignment.
Or, he could direct the military to black bag 3 conservative judges. The body that would judge would favorable towards this.