Vetting a sub: How do I let them down slowly?

Hi, so I'm a dom-leaning switch and Im vetting my first sub online and we've mostly been talking. I really like their personality and the stuff they are interested into but some of our values don't align, also I don't think I'm physically attracted with him at all. I want to let him down slowly/softly, since I do like him as a person, we're both inexperienced and he has some insecurity issues. But not sure how'd to go about it, he messaged me on a BDSM server we're both apart of and I think he's really taken with me and I don't want to majorly hurts him with the real reasons. We both want long term partners and exclusive but from the start we're in different countries so it was gonna be long distance, which is difficult to begin with but I was fine with since we kept up communication so well so far but yeah.

Anyways, I'm thinking of maybe doing a small session with him and confirming further whether it's the values/appearance before just say afterwards that I'm realising how important physical contact is for me as a love language, and that the long distance I don't feel will work long term, and that I feel this will just cause more problem then good in our relationship. That I think I want someone that I can spend time with in person and make physical contact with.

What do you think? What else should I think about? Or say? Or going about the situation? Let me know your thoughts, and if it's ok to be a little picky with appearance because the BDSM community isn't that mainstream if you get what I mean. Like he does tick boxes being within my age range and other things but I didn't see anything really long term from the beginning like more then 6 months at most and just planned to be play partners for while, even without knowing his appearance. I don't want to lead him on any further, and I'm thinking I should maybe participate in munches instead and just learn online then do anything else in the future.

Edit: Thank you for the advice. I don't want to be manipulative at all and I do care for him but I don't want to play. In this situation it's best to be honest even though I want to avoid being harsh. Anyways, I'll be honest with him about the long distance thing and focus on that, than you for the advice. I'm sorry to hear about some of your experiences, and i hope you're in better place now and getting the care you deserve ❤️