downdog - a mother's milk production has very little/nothing at all to do with her own intake of food or the quality of her intake of food. Ditto drink. Ditto rest. It's an unhelpful myth to perpetuate, sorry.
somethinganything - none of the bf lines should lecture you on the use of formula. I am a bfc with NCT - I didn't lecture you, now, did I ?
Without being there at the time, I can't tell what happened in the early days. It may be, though, that your baby was not transferring milk effectively despite the frequent feeding, and that this was missed (not an uncommon tale, sadly).
On the other hand, it may be you are one of the rare women who does struggle to produce sufficient milk - and I do see that expressing 6-8 times a day plus at night is an enormous task. The thing is, though, that this is the only way you will rescue your milk supply - formula top ups at every feed are the death knell for any breastfeeding at all. The majority of women are simply not able to maintain (let alone increase) their milk supply with top ups as often as this It is possible to breastfeed and use formula alongside breastfeeding, but the formula has to be limited - top ups at every feed don't allow breastfeeding to continue longer-term
You might get away with fewer expressings - try four, plus at night, perhaps, and see if this makes a difference?
I hope this helps. Like you, I think honesty is important and you can then make a decision based on facts.