I thought about your question earlier, and unfortunately do not have a ready answer for you... I am just amazed how high you were able to "work up to" in relatively short amount of time. Wow, what a trooper!
To me, dosing is a very subjective thing and there is no hard and fast rule about it.
I would say, given your record, try to go one drop more each time, just make sure you have some vit C handy, so if the herxing (detox) symptoms get to be too much, you can counter-act it with vitamin C on the spot... and then of course you will know NOT to increase the next dose.
And then of course, as this is no one-mile-dash race to the finish line, you can also just take it slow and go one drop at a day... it really is just up to you.