I am glad the appt with your IBCLC went well. I think you have answers now that make lots of sense.
I DO think your LC is being a mite cautious in suggesting you have to do this or that until the one month check up. This is common when weight gain or output was slow at first, of course everyone want to be cautious and make sure baby is getting enough. But breastfeeding changes RAPIDLY in the early weeks, baby’s latch improves, moms start to figure it all out and start to relax, and, mostly, if baby is nursing frequently & effectively enough, milk supply increases and increases as it should (Then is levels off or "regulates" at 5 or 6 weeks or so and mom makes basically about same amount per day for the rest of the time she nurses (going down very slowly as solids are introduced after 6 months.)
Your LC said you have forceful letdown. Now, this does not mean you have oversupply too. But forceful letdown is unlikely to be present if you have low supply. Forceful letdown would cause the symptoms you describe in you baby.
If you stop or lower your fenugreek intake, and your milk production is dependent on the fenugreek, that will lower your production. But frankly I am not at all convinced your milk supply needs now or every needed the boost fenugreek gave it. It’s just so early to be diagnosing low supply especially when your baby (as I understand it) had latch issues that made milk transfer difficult. Yes, over time, latch issues or rather, poor milk transfer, can harm supply, but I hope you are starting to see improvement with latch and milk intake?
The single best way to make sure you have enough milk production is frequent, effective milk removal. If this is happening, few moms actually need galactagogues to keep up good production.