This may not be an option for him. Long distance relationships can be hard on almost anyone. While you seem to be confident in what you want (kissing flirting exploring your sexuality without sex) he may just not be able to understand this. Does this mean he does not trust you? I would say yes and no. I think it is more accurate to say he does not feel that flirting and kissing can just stay “friendly and harmless” or explorative in nature. Some people just feel these actions are not casual, and even if they are at the start, they will turn into something more. Combine that with the history of his ex and he feels like he will soon lose you to another. That can be very scary!
As for his apparent contradiction… He does not see two women together as a threat to him, if anything it is probably something he finds very attractive and would love to watch or get in the middle of. A man on the other hand is a direct threat. That man is not erotic to him, he is a potential replacement to him. Now I know as a bi curious person that woman could be a legitimate sexual replacement to him but that is not how his brain his wired. He is wired to think you want a man, not a woman, so even if she is a threat, he just will not have as easy of a time seeing it.
The thing I see here is that you seem to be more sexually adventurous than him. He does not seem to be interested in sharing his bedroom with others or exploring his sexuality as you are. This could be a sexual incomparability you will have to deal with. Do you need these sexual encounters? Do you thrive with this exploration? Can you see yourself dedicated to one person? Is that what he wants? I know it may sound more surprising to hear that a man may not want to kiss or be with other women but it does happen… not everyone is able to have an open relationship. It sounds like you need to talk to him about what kissing and flirting means to him, is it something that can be casual, or does it, in his mind lead to more? Does it hurt him to think you need more than what he can give? Would this only be while you are so far apart? These are the things you need to talk to him about.