Once again, I reckon toomany has given you some sterling advice, OP. I would definitely go with your instincts and the advice of the ABA rather than your MCHN.
I think at around 6 weeks old I found that circadian rhythm thing kicked in for DD and she slept for a good period overnight. She was confused between day and night for the first 2 weeks or so. After that, she gradually slept for a longer period at night (between 3-5 hours) and woke more frequently during the day. Your bubs will work it out
Sounds like you have plenty of milk, and if it is the advice of your MCHN that's causing the confusion about whether or not your milk has "come in", just don't worry about it! I'd be ignoring that advice, myself - it kind of goes against what people who are interested in making bfeeding work advise.
Congratulations on doing so well! You sound like you are going great guns!