How much could I keep if I withdraw a rollover-IRA early?

A little less than half. When a married couple has $612,351 or more of taxable income, including the IRA withdrawal, in any one year, the federal tax rate is 37% on some of the income; the average is less, but probably still over 30%. The federal penalty is 10%. California tax is going to be about 10% as well.

You can considerably reduce the tax by withdrawing small amounts each year for several years, instead of doing it all at one time.

Or you can avoid the federal penalty by taking substantially equal periodic payments instead of a lump sum.

Or, if you are going to do it all at once, moving to a state without a state income tax before you withdraw it would save you about $100,000, or whatever the California tax is; more than enough to cover your moving expenses.

About 60% of it

You will lose more than 50% of it.

Get professional help, you can clearly afford it.

Somewhere around half.