Going in reverse order
4 - You can think of Social Security as part of your bond allocation, so your portfolio is more than 20% bonds. Probably enough, imo. Some people target 60/40 as a retirement portfolio.
3 - Money is fungible - bonds are bonds.
If the market drops and you want to rebalance, you can do it in the pre-tax or Roth accounts.
If the market is down and you want to spend bonds to allow the market to recover, you can sell stock in your taxable account to get cash and then trade the bonds for stock in your retirement accounts. Asset allocation is the same either way and the trades are tax friendly.
2 - SEPP is less flexible than Option 1, but certainly a good option
1 - How to get $30k - just take it from the brokerage account. You have 10+ years of runway
You get the standard deduction (~$25k) AND a large 0% tax bracket for LTCGs (~$80k) so total income of ~$105k before LTCGs are taxed
Having health insurance premiums independent of AGI is a very nice thing to have, so that does give you Roth conversion opportunities. Roth conversions AND LTCGs are taxable at the State level in most states, so just be aware of that.
So...
$30k W2 income
~$5k in dividends in brokerage account
~$15k in long-term capital gains (selling $30k of VTSAX assuming it has doubled since you bought it, for example)
This leaves ~$55k of wiggle room for future tax optimization.
You can cap gain harvest next-year's sale of $30k of VTSAX
And do a Roth conversion to fill at least the 10% bracket (~$15k Roth conversion), maybe some 12%. With "only" $650k in traditional accounts you may never pay more than 12% tax. 12% now or 12% in 20 years is mathematically the same so no rush.
https://www.gocurrycracker.com/is-your-401k-too-big-part-2/This calc can help you figure out the right numbers
https://www.gocurrycracker.com/federal-income-tax-calculator/Example with $15k Roth conversion
