So sorry OP. Many of us have been through it but you can and will come out the other side. You will have a great relationship with your DD and yes a different family, comprising your chosen friends and relatives.
He has repeatedly shown you who he is, believe him. As you say having your life partner gaslight you is an awful way to live, it makes you feel like you are losing touch with reality, I used to say it was like living on a wobble board where the ground beneath is constantly shifting.
Try to minimise your expectation of answers from him, you won’t get accurate ones.
Please also know that men who behave like this do have something missing in their soul. As someone said on another thread recently the gaslighters and the cheaters are often the cup -half -empty types. I bet your DH behaves like this, as he has some internal discontent eating away at him. All an OW does is provide an opportunity for them to temporarily reinvent themselves. For a while they can pretend to be a better version of themselves.
The family and life that you offered him was good, but he does not deserve or appreciate it. You did all you could.
Focus on yourself and your DD now build happy memories, you can start now. Order some new cushions, and bedding, watch a film with her, get a pet you’ve always wanted. Small things that symbolise better chapters to come.