There are soooo many issues with your relationship, so it doesn't matter if he has done anything that you can specifically point out as being something that he's done wrong. Even if someone is perfect we're still entitled to end relationships if we're over them anyway, but there are so many things that are wrong!
You don't want to kiss him and you have sex with him only because you're giving in. You might not realise it now but that can cause long term sexual trauma going forward. It's HORRIBLE to have sex with someone when you're not into it anymore. Don't do it to yourself anymore please!
When you don't give in he turns over and huffs and puffs, ugh!! What a turn off sexually but also towards him as a person...it just makes himself look pathetic and childish and wants to make sure you give in again in the future!
He doesn't want to discuss anything to do with planning for the future, buying houses etc. I do an online full time degree...and even though technically we're suppposed to do 39 hours a week, the work load is nowhere near close to that, so there's no way that he's spending that much time on his part time course and unable to help in any other way!
He storms off and goes off crying until you smooth things over? Oh my god!! He needs to get a grip. If he is genuinely that emotional and can't deal with arguments then that is his issue, he needs to go and learn some coping and communication skills so that he can handle arguments. This is not your issue.
It's not cruel to end it and you need to get that out of your head!
So what if his family resent you, they might not anyway, but even if you got on great with them after the split they could still turn on you after or if he meets someone else so that shouldn't even be a consideration.
You say the kids will be so upset, the thing is they might be upset during the adjustment period, but they adapt, they always do and they'll be perfectly happy :)
When I ended it my ex ran upstairs and blurted it out in an awful way to them and I didn't get a chance to handle it properly, so I do understand your concern about him getting emotional and leaving you to deal with it, but the thing is you can't control how he's going to act or respond or what he's going to say to the kids. That's not a good reason to stay.
Work out what you intend to say to the kids just in case he does run off crying trying to make you look like the bad guy.Have something ready to say just in case and you will feel a lot more calm about it.
If you're waiting until the lockdown is over would it be possible to have someone mind your kids on the day you plan to tell him, that way he won't be able to have a tantrum in front of them!