This may not be the answer your looking for, but here goes...
As far as trying to get others in the house to help out, stand firm. Make a list of house hold chores. Morning chores, make your bed, get your self ready Etc. Evening chores, make sure all of your messes are cleaned up, do your chores that are on your chore chart, sweeping, laundry, kitchen Etc. Sit down with the entire family and assign chores according to age and maturity, rotate chores that can be rotated. Don't expect you 5 year old to be out mowing the lawn, but your 15 yr old and husband can take turns.
Your 15 year old not being able to make his own breakfast, let alone know how to make breakfast for the whole family, not so good. Your future DIL will greatly thank you for teaching him to be helpful around the house and him not expecting her to do all of the work since that is what he expects of you right now. There is no reason, other he has become completely dependent on you, that he is not doing chores already. My son is 8, he unloads the dishwasher, switches the clothes from the washer to the dryer and starts the dryer. He is great about cleaning the living room when I ask him and with out question, gets himself and his sister, 5, a bowl of cereal for breakfast if we have nothing else planned. He also vacuums his own room. They both are responsible for keeping their own rooms clean. We have one day a week were we completely clean the house, vacuum, mop, dust, clean bathrooms and they are in every room with me doing their part to clean. The rest of the week is just maintaining, picking up toys, spot mopping. They did not get to that point by me just telling them, go do this. I have worked with them for years and, with a smile on my face and love in my tone, taught them how to do what I need them to do well before I expected them to do it on their own. Sit down with you son, list to him what are neccesities and what are privaleges. You ARE responsible to make sure he has good food to eat, but pizza, candy, cakes etc are a reward. You ARE responsible to make sure that he has clothes to wear, but having any form of designer clothes is a reward. He does need some contact with the outside world, but since he's in school all day, any form of extra curricular activity, and that includes stay with a friend, going to the movies are all rewards. And ALL of these rewards need to be earned by doing his chores and doing them with a good attitude. But at his age, you need to be firm, but don't have the attitude that 'I've cleaned up enough of your stuff, it's time you pulled your own weight around here'. You need to talk to him one on one and explain to him that these are things at his age he needs to learn. Give him choses at to what chores he would like to try first. Sorry so much on this subject. I just finished writing a book child training, so this one is near and dear to my heart.
As far as you going to work to take care of your own wellbeing, and some other remarks you made about your marriage, it almost sounds as though you have giving up at home. That everyone has their own separate lives and just tolerate each other when your all home.You husbands life is work, your life is the house, your 15 year old's is school and entertaining himself and your 5 year old just happens to be there for the ride. My concern would be that when you go back to work, you guys will be even more separated.
I was just in the opposite situation as you. When my husband and I got together, we both worked during the day. Right after my 2nd child was born, he got a better paying job, but is working 2nd shift. Not to long after that, my company shut down all 5 of my stores. We made the decision for me to stay at home until my son was old enough for school. A few months before he was, we then made the decision for me to stay home and homeschool my kids so that we would have a close family relationship. Yes, I have sacrificed a lot. I don't go to the salon, I don't get mani's or pedi's, I don't have a closet full of designer clothes, I barely have any jewelery to speak of. I pretty much gave up on my career. But, my family is very close. Had my kids went to school, they would only see their dad 1 to 2 days a week. That's not enough for us.
I think you have sacrificed so much for your family, doing for them. But you missed one key element of being a parent. Teaching them so they learn to do it for themselves and then for others. You wouldn't do your kids math homework for them would you? You would help, teach them how to do it so they know. That's what you missed with your oldest.
As far as your marriage, when you start looking at him with this "What are you going to do for me to make me happier or make my life easier", that's when things get real bad real fast. I suggest a book, Have a New Husband by Friday. It's real good.
Good luck to you.