Unless your DH does some kind of shift work which means he wasn't in bed until 5am or something, he needs to get up at a reasonable time to do his share. You're exhausted and you have no idea what's reasonable; he should be stepping up and giving you a break, not imposing more things.
Here are some ideas: he wants to go out and get stuff. Let him. He can take DS, and you can stay at home. If the housework is really getting you down (and I know what it's like when people say "forget the housework! You have a baby!" - that's really no helpful as no one wants to live in a tip!), do it then.
He gets back and wants to work on his hobby. Ok, give him an hour. Then he takes DS so you get time. They can watch the rugby and you can nap (unless you especially want to watch it too), or do what you fancy doing for a bit.
Tomorrow you go to church, and speak to the minister about getting help with Sunday School. I know it can be nice to do something like that if you're at home all week - it can be something different and you feel useful. ok, as long as you want to do it. But not every week. The church needs to pull together. You should not be doing it every week in any case - you need time in church too, and the children need to get to know more than one person. Three hours is also a lot. Can you maybe have the children stay in church for part of the service (even to colour in or something)?
I would suggest you say to the minister "I can't keep doing Sunday School every week. It's not fair on me or on the children. Can we look at creating a rota for others to help? I would be happy to coordinate that and train a few people up to take it in turns. It could make this much better for the children too, as they will get to know more people from church. How about involving the children in the service once per month as well, so that Sunday School is shorter on that day? They could sing some of their favourite songs for the congregation, or do some Bible readings / prayers / help with lifting the offering."
Set a good example by involving others, not by trying to do it all yourself. What will the children think if they grow up seeing the one person they know from church looking frazzled and fed up because everyone lands everything on her? Is it not better for them to see the church family pulling together to support each other and enjoy being together?
There are books you can get which contain ready-made lessons. We use them and they're good. At first I was sceptical because I thought it was better for us to prepare our own lesions, but once we tried them we found them excellent! I'm sure you can find them online, or people here could help.
You sound like a lovely mummy who is doing a great job but could do with support - don't be scared to take help. You will be an even better mummy if you get some rest!