Kazzi - typed a message last night, but lost it. Much of what others have said here.
First be very proud of what you do achieve with them. Having three is hard work when so young, so anything you manage is a result. Have you considered them having school dinners so you don't have to cook in the evenings?
Anyway, try and make a fresh start - homework should definitely not be a stress, and if it is, it will be counter-productive. Try and make the reading a really special time - maybe snuggle up in a big bed together with the older two after their bath or something, and give them a sticker chart to reward them if they read without complaining. I do think reading and being read to is one of the most crucial things at this age, but it MUST be a positive experience. If they are very anti-books, then try you reading to them for a bit, some favourite picture books - it's all positive stuff. Once they get into a positive routine I'm sure they'll start to enjoy it.
Chat to the teachers about spelling strategies - our school has fantastic ways of teaching spelling - really innovative, and make spellings fun. I'm sure they don't need to be a stress. Pin them up, with flashcards, around the tea table, and talk about them then, then maybe 'test them' over breakfast.
Hope you manage to turn homework into a more fun time for you all.