Working together and living together is enough to put a strain on any couple, even before you factor in 4 kids and their needs.
Some of the things you mention though, ie TV, phones, working out what the kids are up to? are they things you really "need" to do, or are you making work for yourself with some of that?
I think sometimes you have to take a back seat, let the kids sort themselves a bit, its not going to harm them, it will help them as they grow up into adults.
Exert your authority at work, (is it your own business?), and change your hours if you can, so that they are more suited.
Dont do DIY, either get him to do it, or get someone in to do it and get your husband to pay them.
If the kids are old enough to be doing their exams, they are old enough to be helping out too, even if it is just their responsibility to cook a meal one night a week each.
With a big family, you have to work as a team, and you can be team leader.. get delegating!!! :)