You describe two issues, one of which is painful sex and the other is embarrassing sound effects when your partner withdraws. You’re wondering why that happens and whether you can change it.
I don’t have an absolute solution for your dilemma, but I do have a suggestion that I hope will be helpful. We consider the vagina to be a “potential space”; in other words, the walls of the vagina are usually collapsed but can create “space” when needed – when you insert a tampon, for example, or during intercourse. When the space is created, air can, as you describe, enter and be trapped; the entering object (a penis, during intercourse) forces the air out. If the space is tight, there’s likely to be that sound effect you’ve noticed.
You may consider using vaginal dilators, which gently stretch the vagina, giving it greater capacity in both width and depth. This should both reduce the painful sensation of tightness you experience and the likelihood that air escaping will cause the embarrassing sounds.
I think this is definitely worth trying. Good luck! And in the meantime, remember that sex for everyone includes at least some messiness or awkwardness – and one of the joys of midlife intimacy can be the playfulness of laughing together.