Help with chastity, denial, and satisfying both of us

Hi all. I’m a newcomer to this forum, though I’ve spent plenty of time in the kink and BDSM scenes. I’m looking for any advice or tips on how to sort out my current situation. I’ve been married for 18 years. My wife has acted as my Mistress before in a non-24/7 dynamic relationship. One thing is certain: she’s open-minded and kinky, just like me. Life got busy, so the D/s stuff took a back seat for several years, except for a short attempt to restart it about a year ago. My wife gets frustrated because my libido has dropped quite a bit. What does get me aroused is being in chastity. She loves feeling deep inside me during sex, but when we have vanilla intercourse, I either shoot too early or lose my erection. I can keep going longer if there’s plenty of teasing and denial, or if I’m wearing an enforced device. We actually worked out a plan recently where I’d be locked up and only allowed to have sex with her while wearing a large sheath that prevents ejaculation. However, this didn’t really do much for her satisfaction. We also tried a bag containing mostly red beads with just a few green ones; the color indicated whether or not I was permitted to cum. I’ve tested out a couple of chastity devices before, but they always caused pain during night erections or were generally uncomfortable in their design. I’m thinking about trying a Holly Trainer or that new 3D-printed model next. The second issue is my love-hate relationship with denial. The problem is that my wife gives in too easily to my whining (which was why the bead-chance idea seemed perfect). Next, how do we satisfy her without me ejaculating? Is there a good method for adapting a strap-on harness to work well with a chastity setup like an HT? I realize much of this focuses on “my” wants and needs. When I ask my wife what she likes, I don’t always get clear answers. She has fantasies about voyeurism, particularly involving me in groups of men and women or just mixed company. She enjoys seeing me sexually frustrated, but that frustration often leads her to want a hard orgasm inside her, which then releases the sexual tension that keeps me responsive. I’m a 55-year-old straight-ish male. My wife is twelve years younger. She isn’t as sadistic as I might prefer, but I feel lucky to have such an open-minded partner. Any thoughts would be appreciated.