Many of my comments may come off as criticism but that's not how they're intended. Your approach is very different from mine, so my intent it more to explain another way of looking at this. I don't mean to suggest my was is any better than yours.
But first, a few mechanical questions. Why do you have a 15% tax rate on your withdrawals from your taxable account? I'm very far from a tax expert, but I wouldn't think you would need to pay the long-term tax rate of 15% (assuming your income is in the right range), but it should only be on the gains rather than the total amount. You also have a 15% tax rate starting in 2038 on your tax-deferred accounts, but I wouldn't expect that tax rate for different reasons. Are you planning a Roth ladder? If so you should be paying less than 15%, I would expect. It's hard to know what's going on with the tax numbers without knowing more details.
You also show a 4% withdrawal rate. I assume you understand that when using the 4% "rule" you do not take 4% out each year, but 4% the first year and then adjust for inflation. You may just be using 4% each year to simplify.
A more substantive criticism is that you are assuming a steady rate of growth (5%). As you know, that's not how markets work. Plans that work very well with static growth rates look great on paper, but just don't match reality. Using an existing tool like CFireSim or FIRECalc is much better because they run lots of scenarios on real historical data.
Finally, once you get below a 4% withdrawal rate, and especially below 3.5% then all the planning isn't worth much. At that point you have more than you need and the planning and optimizing just doesn't add very much.
And the obligatory facepunch. Holy crap you spend a shit-ton of money! If you could get your expenses down from insanely high to just very high you could FIRE much sooner than you're planning. I'm assuming with those large spending numbers you have a mortgage; are you planning to pay it off or are you planning to keep it forever? I'm assuming the latter since the spending doesn't drop much until you're 80.
I kept a spreadsheet like this one early in my FIRE journey. Ultimately I found that each year something was so substantially different that I had to re-do it frequently. It didn't add much value for me. Once I had 25x my planned spending and I had enough to get my Roth ladder going, I basically pulled the plug. None of my forecasts were accurate on the income, growth, inflation, or spending amounts. I found I just wasted all the time I put into the spreadsheets. The time I put into lowering expenses is what had a substantial impact for me. My initial spreadsheets had me retiring at 55, then 50, then 45, and I ultimately FIREd at 42. By cutting expenses we saved more and needed less, and that's what got us to freedom sooner than planned. I feel like I'm living a FatFIRE lifestyle, but I'm closer to half your spending amounts. But maybe you have 10 kids?
