Welcome to the forums, and you've done great reaching out to the forums for support.
Sorry to hear that you're having a hard time with your relationship at the moment. It seems you've been taken on an emotional roller coaster ride by how your partner is still being in contact with his ex wife (and in the past, his ex girlfriend). You've also voiced out your concerns to him about how for him to still be in contact with his ex-wife, is making you uncomfortable, which is good as communication is key to maintaining a relationship.
I want to assure you that, your feelings are valid, and I can understand why you feel that there's two sides to him. On one hand he is a loving and generous fun to be around person who treats you like a queen. It's great when we experience love and affection from another person, and it brings out a lot of happy and delightful times together with our partners.
On the other hand, your partner may have unresolved feelings towards his ex-wife, and is using the opportunity to help her with maintenance around the house, as a way to confirm his feelings. If he has truly moved on from his ex-wife and is completely committed to being in a relationship with you, it is as you said, his ex-wife will have to find other ways of living her own life without him in it (especially since she initiated the divorce, so she'll need to own up to that responsibility of choosing to live a single life). Your partner also needs to understand why you're feeling this way and work together with you (he'll need to express his feelings as to why he's still helping is ex-wife, and why does he think you're feeling jealous), rather than calling it 'jealous' and dismissing your feelings and concerns.
I do feel for you, and I feel you deserve better if your partner is not willing to work things out with you. Please take care of yourself first. Happy to listen to you more if you'd like to chat.