Does he have some form of disability or something that means he's unable to look after the same two children you look after?
He has no issue leaving you to solo parent all day every week but is incapable of doing the same thing?
Nah YANBU. You would be unreasonable if he was a hands on parent and rarely went out. He goes out all the time and doesn't look after his own kids.
You are lonely, exhausted, you need support. You're a single mum, who also cleans up after another full grown adult.
All parents in a house should get the same level of free time. Always. Very simple rule. And as much time as you spend socialising with other people, you spend equal time connecting with your partner. Very simple. If there isn't enough time for you to have the same amount of free time as he gets. He's taking too much. If there isn't enough time to spend the same amount of quality time together as he spends with his friends, he's spending too much time with his friends. Very simple rule.
I saw a woman talking about how she manages her finances. If they want to buy a luxury item then the same amount of money goes in savings. If you can't afford that, you can't afford the item.
If he wants to go out with his friends then he carves out the same amount of time both for you to have alone and for you both to have together. If he doesn't have time for that, he doesn't have time for what he wants to do. It works on the same time frame. If he goes away for 3 nights once a year, then once a year you have a weekend together and you get a weekend alone. If he goes out for a full day every week then every week he spends a day with you, and every week he looks after the kids for a day so you can have a day doing what you want. If there's not enough time for that, then there's not enough time for him to go out for a full day every week. Simple.