Very interesting discussion, thank you for presenting it! I may be getting a little confused between all the charts, so hopefully my comments will be valid and correct.
Early on you mention the ASC/DES being "flipped" between you and the first lady, and the moon's in opposition. The ASC/DES in this type of aspect literally would indicate that what you are looking for in a partner/marriage relationship (your descendent) is precisely how she presents herself, and vice versa, she sees in your Ascendent what her descendent is looking for, and this is a very strong and compatible tie, and enviable. The opposition of the moon's is up for discussion, as this puts you both in different places emotionally. In your case, the cancer moon looking for sentimentality finds a colder and analytical emotion coming from the Capricorn moon. This could work, depending on the other aspects, and also because it is rather weak here, being 10 degrees apart.
A quick look at the synastry chart shows your mars on her moon, pulling you sexually, she seems very feminine to you and stimulates you. However her mars is semi-square with this, so very fiery physical attraction, but these two mars positions will be setting you both off emotionally, with some sparks flying and hurt feelings. She natally has a mercury/mars conjunction, so she is a quick thinker and can tend to loose her temper. And we find your pluto churning up this energy! This is really a strong pull, but on a daily basis, living together, you will want to have time to distance yourselves to avoid explosions and blow ups, while maintaining the physical attraction positive side.
Capricorn moon will find itself squelched by Saturn, and Saturn will always win because the moon is in its fall in Capricorn, while Saturn is at home there. Coldness and emotional distancing.
As mentioned already by someone else, the mercury/saturn and mercury/pluto are neither inducive to communications, which is a fundamental necessity in a relationship, once you get out of bed and start living life together. In addition, both Venuses are squaring the other's mercury, so you have difficulty sharing your ideas, you are on two different wave lengths!
And the cherry on the cake is the sun/pluto that is very bossy, very transforming and can be overwhelming.
Lady number two? Closer in age can be a positive or not. The stellium in the descendent is very compelling, but the Uranus/Pluto conjunction is a warning signal!
In the synastry here again we can see the moon/mars theme playing out, but in this case the moon's are together, so sympathetic to one another. And the mars is physically drawing you together. And once again, the moon/saturn is present. (coincidence?).
In this synastry however, the sun's are almost perfectly trined, and both aspecting each other's Jupiter, two aspects that can bail you out of a lot of tense situations when they come up! Understanding, generosity and tolerance between the two of you.
Neptune is also involved here, adding a dreamy, romantic quality, and idealism to the relationship. This is carried out in the mercury/neptune conjunction. These are nice aspects, so long as the illusion doesn't turn into delusion.
Then there is the mars/saturn in this relationship, that sets you off on different goals, and in a partnership where you are not pulling together but one against the other, one pushes the other pulls. However, you have this contradictory mars/saturn energy in your natal, so it may be a type of energy that you are used to living with?
So how do the ascendents work out? Her Jupiter, out of sign, is on your ascendent and will certainly make you feel like the world is your oyster, you want to express yourself to your fullest, she makes you expand and beam!
I don't see the ascendent degrees but it looks like late degrees of Leo and aires, which is a trine, and very compatible. Two fiery personalities.
The Leo personality with Aquarius on the descendent needs breathing space in a relationship, while the aires with libra on the descendent wants to be in a close partner relationship. There is a close Venus/saturn trine between you two, so you can work this out fairly easily.
With her sun out of sign but on your descendent, which is also a very strong tie considering your ascendent ruler is the sun, she gives a "sunny" quality to the partnership that you will find very attractive and it is a type of energy that you recognise very well. That Jupiter is also her sun ruler.
Your natal moon, indicator of the type of woman you will tend to seek out, is with Jupiter and Saturn and opposed to mars. So she will be serious but jovial, and also spirited.
This lady has her moon in serious Capricorn, Jupiter is her sun ruler, and her ascendent is fiery aires ruled by mars. No wonder you are drawn to her!
I do hope I haven't mixed up the aspects between the wrong charts, but as I wrote earlier, this comparison really is extremely interesting and intriguing and I did want to offer whatever insight I could, so hope it is ok, and I apologise if I wrote too much.
The final choice of course is in your heart, but please let us know how it works out!