E.,
Welcome to Mamapedia.
First of all, let me suggest that if you are using your real name and real home town, that you not put your children's real names and ages on an internet forum. Not good from a safety standpoint.
Secondly, it's important to do something when you are this happy and unsatisfied - get out, or get counseling. In fact, even if you are considering getting out of the relationship, you still should get counseling. If he won't go with you, go alone.
There are some things that can be done to increase bonding - the people across the street from me have 3 kids, and when Dad is out in the yard, they are too. He rakes, they rake. He puts the leaves in a pile, they shovel them into wheelbarrows or onto tarps and tow them to the woods to be dumped. They spread mulch, they shovel snow, they help wash the cars. While they are out there, they put up some soccer cones or a t-ball set up, and they all play. The question is, will that annoy your husband or make him feel like others understand that there is work to be done?
But this is not a new situation, and you are absolutely not in the same "place" as your husband. You have entirely divided workloads, and that breeds a whole lot of disrespect.
And in your SWH, you say that you are "not working." Yes you are! Change your mindset on that. You are working 7 days a week with no time off. If your husband doesn't view what you do as work, then he's not going to view it as something deserving of his respect, and he's not going to participate in it. In his mind, you have the typical 1950's division of labor - he goes to a job, and comes home for down time or yard work time. You have all the inside work and childrearing. If it worked for you two, that would be one thing. But this is not a successful marriage partnership and so you need professional, objective assistance in sorting it out. Ask your physician for a referral to a counselor who accepts your medical insurance, and start going.
Separation and divorce are not easy and shouldn't be taken lightly by anyone, but your situation is even more complicated because the oldest child is not your child biologically or legally - so even if you and your husband split up and you have custody of the 3 younger kids, what happens to the oldest? This would be very traumatic for the children so any decision needs to be entered into carefully and with full preparation. Maybe the sheer thought of that will make your husband sit up, take notice, and learn to make some changes. Maybe you will learn some new skills too, because you have been a part of letting this situation get to this point. I'm sure you have both complained to each other, but that's not the same as making meaningful joint decisions about the direction of your marriage and family.