You can always drop the DF and see if it makes a difference. For me, the DF was a disaster, DS was up every hour or two with gas and he hardly took anything anyway
I just think that my LO got used to weak sucking.
Try the breast compressions and see if it helps with his frustration at the breast. I don't think block feeding is for you, but breast compressions, I'd back that any day of the week in your situation
You could also add more good fats into your diet - nuts, avocados, etc. to beef up your milk a bit...
I just think it's genetic and I wish the doctors and nurses will understand that some babies have their own curves.
You can always come here for reassurance when you've been beaten up about it
We've got healthy babies who are 98th centile and others who've dropped off the bottom of the charts but they're developing, meeting milestones, etc. FWIW, My doctor was so worried about DS she wanted me to go in between the normal checkups because he was not gaining what she thought he should. She met him at 12 months and I asked about his weight gain and she just said she didn't think it was an issue any more - he's meeting milestones ahead of time and clearly not missing out. The reason doc's are concerned about weight gain at this age is in case it affects development, so if he's developing as he should be which he is, don't worry so much.