I have no clue how single parents do this as normal life.
They don't pile on things on top of each other. You are in the 99th percentile of activities. It's one thing to have one sport for each kid at a time but to have 2 or 3 or 4 things for each kid piled on top of each other. It's almost like you are trying to balance all the kids that specialize in one thing by doing everything. hahahahaha
I am exhausted just reading about everything your kids do. I thought we were busy with never having a break but we didn't have multiple teams/sports/etc going on at once. Daughter had soccer and softball and son had soccer, basketball and baseball. Only one team for each sport and only a cross over between sports for maybe a week or two. You can limit things to keep your sanity. The bad part was missing one of the kids stuff because both kids had stuff going on so we had to divide and conquer between kids/parents. It was a great thing when one of the kids had a weekend off so both parents could watch one of the kids games. There were a couple summers where we were gone every weekend for 8-10 straight weeks.
I would likely try and limit the multiple obligations during the same season for everyone's sanity.
I feel like swim, which adds on through the year may end up ending or a season being skipped. Which I really dislike but it is easily the least favorite sport of my boys and is a big time and effort commitment for them. I hate the thought of it because my older son has so much potential in it and the HS coaches already know who he is (my SIL was talking to the coach and it came up and she was surprised... I as well as we haven't had any contact with them and I don't think they are ever at any of our meets or anything) and the conditioning he gets from it with such low risk of injury is unbeatable for him with his other sports. Though I would encourage them to keep at it, I am not going to force them and I get the sense the older one is very close to ending it. If the older one does, my guess is the younger one will follow his lead. If that happens, things simplify a ton.
It is a lot. I know it seems like I push this all on them but I don't. I do enjoy my kids doing whatever they are doing- I much rather go to my daughters vball tournament than watch an NFL game or whatever else. For me, the time/energy is well spent and enjoyable. I do take care to keep the kids balanced and that they have plenty of time to do whatever that isn't sport related. I never make them practice at home or anything because they do need that time (though I still wouldn't make them but I would push/encourage it a whole lot more if they were not as busy).
I give them 'days off' of not having to go to practice before when they needed it. A lot more recently because of everything going on.
This may be the last year of my daughter doing club/school vball at the same time as she goes to HS and I think there are rules on how club/school works that they basically can't do both at the same time. I don't know, I will have to find out more info on that soon. Other than that, she has played basketball but I don't know if she will even try to in HS and if she doesn't play for school she wouldn't play outside of school. She did mention she had interest in doing flag football. But we shall see how that unfolds.... but overall, things will change with her after this year.
My older son, with the swim, is usually the only doubling up he has with football and basketball.... and football there is no doubling up as he just misses the start of swim season until football is over. Basketball takes priority over swim because he likes it much more and I coach it. In spring, he did do soccer and track last year but soccer for the school is almost like zero time commitment... they have done like 4 practices in 3 years total and many of the games get rained out or the field is muddy, but it scratches his soccer itch. Track has a few practices right after school so the only thing for me is having to pick him up later and then meets which there are not a ton of.... I think 4 or 5 from last year. He did say he wanted to do volleyball this year. And I don't know what that looks like for boys.
My younger son, is similar and swim is the big thing. He started BJJ but that is pretty flexible with practice time and there is no commitment to compete unless we want to. Other than that, he will do school football, basketball and then soccer a couple of years before he can add track or volleyball if he wanted.
As long as it isn't too much for them and they are enjoying it then I am fine with the hectic nature of it and making it work. This is a season in life and when it is gone, I will miss it. In "normal" times with the wife, it works out pretty well. Right now, just a little harder to keep on it.