Orange, what you're really asking is what number you need to feel secure that quitting your day job and shifting to self-employment is going to work for you. It's not necessary to achieve FI yet because your business is going to earn you well over your expense requirements.
When I did this, I saved up enough to cover six months of expenses (in a savings account - didn't count my retirement accounts in this). My business cash flowed from day one, but I knew that I needed to get the pipeline filled with enough work that I'd be insulated from disasters - late payments, canceled projects, whatever. I set my trigger at six weeks of expenses, figuring that it would take a little while to find a new job and start getting paid if things went South. Got to eight weeks at my low point, and that lit a fire under me for sure.
Having been a follower of your journal for a while, it seems to me that you've been keeping the W2 because it's low-effort and you can multitask the business and still bring in your W2 income. Recently you've had to ramp up the job commitments, which is probably taking time away from what you'd rather be doing.
Do two P&L estimate scenarios for the next 12 months, one estimate if you keep your W2 job, the other if you quit. Compare these and see if this helps clarify your next step. Then make sure you have enough cash to cover expenses for x months, and decide whether to pull the trigger. You could time this around events in your business, too.
You might also consider a halfway step where you reduce your work commitment, but don't quit altogether.