Hmmm..... this feels like a bit of an over reaction thread.
OP, I am not saying that what your partner did was ok- definitely something that needs moderated/ corrected....
But it's a little hard to tell from this how truly bad it was.
Certainly if these things were done in uncontrolled anger then that would be terrible. But I also think it's perfectly possible that someone can be rough housing and/or having a less molly-coddling approach to parenting, and misjudgments can be made when adapting to a different parenting style and kids brought up a different way.
OP, It does feel like you and your children are very easily upset. Is it possible you deal with things and protect them in a way that increases anxiety, rather than builds resilience? (Crying for ages, and you crying too, over a 13 year old kid ending up in a swimming pool, surrounded by people who could help him out - (was it even out of his depth?) and a kid, who had repeatedly refused to share, being really upset and getting lots of comfort from you about a ball knocked out of his hands.... just all feels very fragile....).
Realize I am inviting lots of flaming and accusations that my standards are low etc etc.... but what I am really saying is that these things can be nuanced and I feel understanding what is really happening here takes a bit more info than we have.
My DP has children of his own and is actually from a different culture, which has a lot of different attitudes to children and how to bring them up. He tries to be very respectful of my style with my daughter (which to him is mollycoddling). But sometimes there are misteps. Sometimes, this involves me being firm about what I believe is right, and helping them mend slight mishaps. Other times, though, it involves me stepping back, despite something jarring with me, and realizing that he is actually bringing something valuable and different, that over time can help my DD build resilience and confidence. My DD adores him - and has learned so much from him - but they also have fall outs because he approaches her in a way that she doesn't always expect. Eg if she were trying to climb a rope with me, I would hover underneath and the second she expressed being stuck or worried, I would prop up her weight or lift her down. But when he teaches her to climb a rope, he stands back and when she says she is stuck and calls for his help, he stays standing back and tells her not to panic and look around her for something to hold onto etc. she complains that her hands are sore and she was scared. But guess what, next day she is out climbing that rope, brimming with pride, and wanting to teach me that it is all about not panicking, and looking around for the next thing to do, even if you think you are stuck!
That may not be the case for you- it may be that your DP is out of control or not a good person and not good for your children.... but I think being sure of that takes more than the gut reactions of folks on the internet....
Good luck. 