Firstly, good on you for being there for her and your kids, it’s still difficult socially for men to take on the fulltime role of carer.
I’m not sure if you’re currently together or separated, you say your single but caring for 3, I assume you meant you’re in a de-facto relationship with 2 children from a previous relationship. However, it definitely sounds like you need a good rest, I know the struggle of not having any support. Perhaps you could make friends with some of the families at school and arrange away time for the children with someone you trust.
I don’t know how frightening people with Bipolar should be, in my experience with bipolar, most of us are a danger to ourselves. Quite a lot of the time people don’t get adequately diagnosed, or don’t admit their full diagnosis to others due to the stigma (something to consider).
The children must come first, please look into age-appropriate support for them, such as a school counsellor or headspace. I think it’s important to teach the children that this is an illness, and people may need to go away, for everyone’s safety. The important thing is to keep the conversation age appropriate, and never criticise condemn or complain about your partner in front of them.
Please stay in touch on this forum. Using the same forum thread ‘Very Lost’ is a great way to get the best support for this difficult situation.