I'd argue there should be a flat out cap on wealth. Nobody should have 500 billion dollars. Not sure what it should be, but somewhere under 500 billion.
Not in the US at the federal level. Taxes are an anti inflationary device when dealing with a sovereign currency. It's the last step of the fiscal year. Step one is literally printing money, step two is distribution of those funds, step three is to allow the money to circulate between businesses and people, and then step four at the end of the year is to levy taxes to combat inflation. They used to literally burn the dollars they collected, now they just zero out an entry in a ledger.
How would you tax a software company that has remote work and runs on someone else's servers?
The land they need could probably be a small single office room and a letter box.
No, no, no. Just like a tax on unrealized gains is a bad idea because of how much it would royally fuck up the stock market, including every 401(k). What they need to do instead is tax the ways used by the extremely wealthy to utilize their gains without technically realizing them, even if that sometimes means taxing debt (aka treating it as income when they borrow against it and taxing accordingly).
They'd just 'devide' up their businesses into a chain of symbiotic entities defined by paygrade. Then the executive level can enrich itself insulated from us front line grunts.