Hi there, it's midwife again.
Happy New Year!
Thank you for the update
It sounds you are having really challenging times however ploughing on despite setbacks. Well done.
From your description, it sounds you really need help with positioning and attachment. Please experiment with a rugby hold position.
In relation to tongue tie, have you seen your baby sticking the tongue out long enough to cover the bottom lip? If your baby can do it, the cause of your cracked nipples is poor positioning and attachment, not tongue tie.
Has someone told you to pump between feeds to increase your milk supply? If it's difficult to tell without full assessment however if your baby was putting on weight and suddenly started dropping off centiles my gut feeling is you don't have an underlying issue with your ability to produce milk.
I suggest you get a good pump and start pumping at least 3 times a day for 40 minutes (10 minutes at one breast, switch breasts, another 10 minutes and repeat both sides again).
Pumps are quite expensive however it has to be set against the cost of formula. With this regime you should see improvement in your milk supply after 3 days.
The idea is to keep the woman's milk supply going until other issues are being sorted out. Milk is produced on a supply and demand basis. As babies grow, they naturally demand more.
You say, you keep feeding non-stop to stave off mastitis. What do you mean by that?