Wow, what a difficult first few weeks ! And you have come through them - you're now pain free and comfortable I take it - brilliant.
The only really effective way of making more milk is for more milk to be removed from the breast. All the other stuff - herbs, diet, fluids, teas, tablets - are marginal in their effect at best. You remove milk from the breast in one or both of 2 ways: expressing, and feeding the baby (as you well know :) ).
Anything that interferes with that being done frequently makes you make less milk. Sometimes, other considerations apply, of course - your own well-being, and the baby's need for more nutrition in the short term.
You have got both those aspects sorted - you are feeling ok, though a bit wobbly and under-confident; your baby is doing well, and shows clear signs of thriving.
So....if he roots and sucks his fingers after breastfeeding, what about just breastfeeding him again? Direct? Not ebm? You won't run out of milk - the breasts may slow their flow, but they are not empty even when you have fed from both sides. Even if they feel empty, even if he kicks up a little fuss and shows irritation, just put him on again...and again....and again...as often as your baby will accept. Not to the point of having a fight or struggle with him - a minor fuss is ok.
If you are not ready to drop the formula/ebm altogether, have a plan - instead of 150 ml a day, aim to give no more than 100 for a few days, and then 50 and then you will be well on your way :)
Prob no need to express at all, by the way.