Hey! I'm here and listening. You're not a horrible Mom and you're not failing.
Toddlers are hard!! Do you have 2?
It sounds like you are in desperate need of a break and almost like a total reset.
Is that possible right now? Can you take a day away (maybe leave them with DH) relax, and try to come up a plan for tackling it?
(I'm not an expert on any of this... just have two of my own so repeating some of the things I did)
Snacking - it sounds like you maybe need to cut the snacks and only offer meals? I had a baby who did this with bottles and ended up "pecking" constantly and this was what HV recommended to me. Let them get hungry. Offer small, "snack like" meals with the things they'd have as snacks, because right now you need to try to build up a routine. Then slowly switch out the snacky stuff for mealy type stuff?
Sleep - I always did controlled crying, which I know some people are against, so I'm not sure how much help I can be.
General - have you heard of 1 - 2 - 3 magic? My mum did this with me as a child, so I naturally did it with mine, and it worked great for both of them who are complete opposites.
It's about getting down on their level, keeping your cool, and communicating clearly with them. Kids (especially ones that young) just have no idea how to process all the massive emotions they're feeling, so as adults we kinda have to help them.
This becomes impossible when we're sleep deprived and stressed ourselves, so it's understandable you feel like you're struggling. You're not though, you're human.
So... try to get a break. If that's not possible, make yourself a cup of tea right now, and come up with an action plan.
Sending support. This will pass! 