Sanguine
I have to say on that specific issue - the 24hr feedathon - it sounds exactly like what happened to me and to lots of other women on day 2-3 after birth. After a sleepy start, babies often cluster feed like mad to build up the supply and the second or third night is often when it starts, only to settle down 2 days later when the supply is up.
And then they often do it again periodically, maybe at 10 days, 3 weeks, 5-6 weeks etc etc.. So leaving aside all the other things, the tongue tie, the dehydration, the weight issue - the constant feeding sounds, I'm afraid to say, normal! The thing is, your baby NEEDS to do it since that is how the milk is made - then when your breasts are producing a larger amount, feeds will settle down into a more regular and spaced out pattern.
Perhaps have the tongue tie snipped will make it lots better - it might be (I guess - you really need Tiktok) that feeding will become much more 'efficient' then and you should get a better feed into him/her...
My '2nd day' has been like this with each baby: feeding for 10 mins each side, change, scream, sleep for 10 mins, wake again, start all over again. With perhaps the odd 45-60 minute sleep in the middle of the day. And this went on for about 36 hours. And then after that I had breasts engorged with milk. some days later this then settled down again and it was much more manageable and comfortable.
But this constant feeding is NOT a sign of a problem with your body, but that the right things are going on. And unfortunately for you, if you have had to delay that feedathon because top ups got in the way, if you want to rebuild your supply, one way or another I think you're going to have to add in feeding more frequently to all the other things you're trying?
/hope you do decide to move over to more BF and get enough support to do so - would definitely suggest you get in touch with a LLL or NCT or BFN counsellor since, honestly, they are (usually) much more expert than most medical staff