Wife on the edge! Only needs the right push. Advice.

Beautiful WIFE is on the edge! I wanted to share where we are now and hope to read some input from others.
I have been married to my wife for many years. She has a conservative, vanilla, shy side, as well as a subdued naughty tease, needs to be taken side. The trick has been that if she does something she feels is naughty, the next few days or even weeks she has severe guilt and over reacts by going straight vanilla hard line. Sometimes it will be months before she will be more adventurous again. She is a damn good looking woman and gets hit on often. 5'10" 140 38-25-34. Long raven hair, nice D cups with big nipples. She knows I am open to her playing with other men as long as they would be larger in the cock department, she would be physically safe, and make sure we have NO secrets. I am average at best. 5" long x 3" circumference. I am much older than her and am now having trouble sustaining a solid erection consistently. I admit I am not to disappointed. As she bucks back onto me and my little guy gets soft and drops out of her she will push my face down between her thighs. I sense her frustration level, needing that hard pounding, it increases my hope that she will recognize the "NEED" for a bull cock. Getting her to be open and vocal, even in the privacy of our home, has been a real challenge. She does become noticeably excited when I tell her about my desire for her to get seriously fucked. Fantasies that really get her wet are: 1. feeling a strange cock grow against her, whether it is her leg, tummy or in her hand, 2. having two cocks in her pussy especially if they CUM, 3. me watching her fuck someone else from my chair, and most of all 4. the feeling of a large cock or two pumping cum into her pussy.
Background: For most of our marriage it has been vanilla with a few spots of wild girl. She has watched porn with a co-worker or two. She has rubbed another guys cock to the point of him cumming in his underwear while in a car on the way to a business meeting. When she got home she called me and asked me to come home early from work. She wanted "fucked NOW" and made sure to tell me how that swollen cock looked in his underwear. She has modeled bra and panty sets for "HIS" opinion on business trips. I do believe her when she says they did not fuck. But these moments are RARE. Afterwards she always slut shames herself.
Recently a few naughty moments and several statements have increased my hope that I can get her to enjoy cumming on a large cocked stranger. While in our pool she has started a habit of sitting on the edge, or straddling her floaty, so that I can finger fuck or lick her to orgasm. She has asked what I would do if I came home and found her being fucked by the pool. She drives herself to orgasm by telling me how much she wants "his" cum in her. Following her orgasm she will TELL me to jerk off for her and likes to giggle as she watches me splooge in the pool. A few weeks ago she pushed me into bed. We stripped each other and she went down on me briefly getting my little fellow real hard. She then straddled me and while grinding on me started asking if I would like to watch her do this to a big cock while I sat in the chair she had placed in our bedroom that day. I of course encouraged her by saying FUCK yeah! She increased her tempo and asked me, if I was watching, would I cum in my hand or on her. Laughing, I said I would probably shoot in my hand from all the excitement. She said she would want me to come up behind her and spray on her ass. Specifically right on her asshole. She said she was curious as to how it would feel. her pumping up and down, stretched to accommodate his thick cock and feeling the moment my cum hit her asshole. Then, as my cum ran down from her asshole onto the shaft of his cock she imagined how slippery his cum covered cock would be. She said the thought of my cum being only for lube makes her HOT. Most of the time when we have penetrative sex she will tell me dirty things and beg for my cum; as if she wants me to cum as soon as possible. Rocking her hips and grinding her cunt on my dick. As I start to pant and my penis throbs she begins demanding I cum in her fast. Telling me that the sooner I cum the sooner she can stuff her pussy with a big toy and use my cum as lube. Last, after begging her for years to feed me our cream pies and her refusing. She has now began to make me cum in her, then tell me to fuck her with a big toy and lick her pussy. I am getting discreet pies now but she is still not comfortable pointing it out or wanting to acknowledge it. She knows, that often, I would rather watch and go down on her rather than fuck her myself. I need to find a way to move this forward. She is Sooo close to taking a big dick balls deep until she is full of cum. I could suggest swinging sites or maybe a close married friend, who I know she wants really bad. Who knows how she would handle that.
Hoping to hear from others who may have found away past this plateau.