mr_orange, my concern is what you want to do with this information. Given your returns, it seems like you are capable of getting substantial returns on your hard money real estate investments. Having said that, quitting your job with the expectation that you will be able to spend 7% of your portfolio's value every year, adjusting for inflation, leaves you with very little margin for error. After all, our beloved 4% SWR is better understood as a 4% real withdrawal rate; while getting a 4% nominal rate of return is one thing, a 4% real rate of return after volatility is another entirely. (You are spending down your principal in some cases, after all.)
Just as concerning is the lack of liquidity in hard money loans. Roofs have to be replaced. Out of pocket maximums are hit. In a genuine emergency, getting liquidity from hard money loans is difficult. You could compensate for this by having a really substantial cash buffer, but that's going to drag down your returns.
Moreover, you might even have a reasonable expectation that you could achieve substantial returns for the foreseeable future. That said, changes in the regulatory landscape could lead to a secular decline in real rates of return for hard money loans. There are always intelligent things to do, but basing your retirement strategy on the ability to achieve outsized returns for decades is really, really risky. Even if you are as good as you think you are, you aren't good enough to make a 7% withdrawal rate safe if new regulations make hard money loans substantially less profitable for individuals such as yourself.
That said, my biggest concern is that capital allocation is just really hard in general - and spending down your capital at an aggressive rate while you are allocating capital to illiquid projects scares the heck out of me. I have no idea how diversified you are, but are you in a position where any single default would wipe you out? You might be inclined to say no, but in a world with a 7% real withdrawal rate (which is really more like 10-11% nominal, after volatility), even losing 1/10 of your portfolio could be catastrophic. More money has been lost reaching for yield than at the point of a gun, and this strategy requires you to be good - consistently - for decades. I also used to live in the DFW area and I'm pretty familiar with real estate in the area. The area has had a decent run and for the most part avoided the worst of the real estate crunch. But a repeat of the S&L crisis would be tough to survive for a hard money investor if your risk is concentrated there.
If you genuinely believe that you can a 7% safe withdrawal going forward, then an additional year worked would result in a 5.6% safe withdrawal rate. One more year would give you a 4.48% safe withdrawal rate. One more year after that, just three additional years, would give you a 3.6% safe withdrawal rate. If you're as good as you think you are, then even a single additional year worked after when you think you would be ready would result in a substantially lower withdrawal rate. And here's the best part: a lower withdrawal rate means that you don't have to be as good.
Holding an index fund is eminently easy. I am really good at spending money that gets automatically deposited to my bank account. I'm good at some other stuff as well - some of which is supercharging my becoming FI. That said, I'm not going to count assets that require me to be good towards FI. I'm more than happy to reinvest capital from much more profitable assets over to index funds, but I will be FI once my dumb money is sufficient for financial independence. The same approach might make sense for you as well.