There are so many variables with semi-RE. In the OP’s situation, you are cutting back your current full time work, to go from a higher savings rate to a lower savings rate.
A big question would be age, (ie how long do you have for have 250K in 401K/to grow?) It’s a different situation at 30 than it is at 60. Do your due diligence regarding medical, as it is probably more important than average in your situation. Also make sure your spending numbers are "real" and account for everything.
IMO, home equity in primary residence should not be counted as part of net worth in a drawdown situation. Specifically, I mean it should not be part of your goal of 20-25X expenses in savings (4-5% WR you said earlier), unless you plan to sell. It is already accounted for on the expense side.
On the withdrawal rate topic, once you have some more time in your SemiRE, I would do some research on asset allocation and find one that you can tolerate for the long haul since your contributions will be smaller going forward. Come up with an investment policy statement to hold yourself accountable. AA isn’t so important in a quick accumulation period, but it becomes very important in slow accumulation & drawdown.
You can always post a case study and get input from a bunch of people on here & see what they think. When I have some time I'll PM you back with my particular situation & strategy to see what you think.
Bottom line, IMO with a little effort you can be semi-Re very soon. I'm super jealous!