DCPhil, first and foremost, Congratulations on a retirement at age 53! Fantastic! Secondly. What a great time to put your money to work over the past 4-5 years. You're portfolio doubled, fantastic!
Now, to answer your question. It will really depend on what kind of investments your portfolio is distributed into. At your position, I would be considering a very low risk type of investment and settle on a 3% safe withdrawal rate that allowed about $75k in annual spending. That will significantly increase your annual budget, allow you much greater freedom to spend as you see fit, and of course, your portfolio will likely continue growing.
At the same time, this will allow you the flexibility to choose how you want to spend the increasing funds that you are in control of. You can spend time deciding where your comfort zone is relative to your portfolio, and if you want to spend a large portion at once, you can accommodate that by reducing your annual spend. You've already figured out the hard part of living within your means. The easy part now, is to decide how you want to distribute it as you age gracefully into the FIRE.
Alternatively, you could divide your portfolio into two separate segments, if only in theory, rather than in reality. Utilize one part as your living expenses and "survival" fund, and utilize the second as your "meaningful ways to spend more" fund.
You're in a position where you could take 4% SWR from the entire $2.5 million, and have 100% success by the time of your death, whenever that may be. You've also mentioned that your spending rate doesn't include Social Security which will, in my estimations, conservatively add 40% to your current annual spend rate.
You're sitting in a fantastic position. I'm glad you've found time enjoy it!