In relationship for 14y, married 10y. one child daughter, 9y
History:
We started dating immediately after we met, it was instant connection.
Soon after we started dating she was diagnosed with hipo-thryeosis, lack of thyroid hormones and she started gaining weight. I was always supportive with her, never an idiot who yells that she is fat but rather a person who told her I still love her no matter what. And I still love her.
She wanted to break up few times, but we always came to peace and stayed.
With her gaining weight I also gained weight, never vent to gym and I was never athletic type.
At y4 I shed 40 pounds with cycling and diet, and threatened her to leave if she starts to weigh more then me (90 kg, she was 85 at the moment and gaining weight). Then, we found out she was pregnant.
We decided to marry.
She never loved my parents, but when they bought us a place to live and kept the contract to their name she was furious, since she thought we should get the property. I never in my life expected something for nothing and was simply grateful that we got our place to live (rent free), instead of renting a property. Last 10y she was putting up this argument that made no sense to me on the table. When my parents visited that was instant argument 'they want to check if their property is kept in decent state' and after the visit she was cold for few days. On the other hand, I never had problems with her parents visiting as often as they like.
Visits from my parents and to my parents were kept to 3 times a year due to me not beeing able to fight one week before and after and kept only to Christmass, Easter and once more during sommer. Visit to her parents were more often (they live much closer) and it was bi-weekly.
She also had episodes where she threatend to kill herself few times after my parents visited because 'she can't cope with knowing she will have to meet them again till the rest of her life'
I talked to my best childhood friend about situation, maybe if he had some other view of my parents but he said as far as he knows it my parents are straight normal simple folks as anyone can be.
6 years ago we started working on second child, and got lucky, but then wife had misscariage in 3rd month, she blames me for beeing too rough on her for eating junk food, and still remembers one sentence I said, that she is also to blame and that all her junk-food eating might be her not really wanting this child.
Yes, I was insensitive at that moment, and I might be jerk sometimes. I appoligize every time I do something wrong, and mean it, but that appology is forgotten, and jerkness os remembered.

Last year I started going to gym, and enrolled her too. She started going one month later, and was regular in gym, as was I.
After few months with little progress on both sides in september she told me that she thinks her coach is super hot, and if she should not be in his group anymore. I said she can stay, and that I trust her completely.
At the same time she started super restrictive diet and with her gym efforts she lost 30+ kg in 4 months, gained a lot on confiednce, and basically became the girl/wife I always wanted her to be.
In November she said she is in love in this coach and that she will leave me. Her plans grew more and more in details and beggining of december I came upon this site and learned few things, started with 180 tips.
Things got a little better, but then suddenly on 15th Dec she stopped everthing, hugging, snuggling and sex.
On Christmass she announced that she wants to use all our saving to purchase a small apartment near out current residence, so I can stay in touch with my daughter. I never hid anything from her, so she knows everything how much money we have.
Last 14 years I have been sole contributor of money to our household, my wage beeing 1.5 of national average. Also I have a company with a small website that generates about one yearly average national income.
When she got pregnant I employed her in my comapny (thinking way ahead, so she could retire early and to get pension), but bassicaly she did nothing for first 6-7 years, and last 3 years she does about half hour up to hour of administrative work.
Now sudenly, after so many years of me trying to get her out of the house (to work or even to hang out with her friends) she started looking for a real job, hanging out with new friends from gym, recconecting to old friends.

Conclusion:
She is obviusely in love with another man, and is determined to leave.
She wants me to respond to her request asap.
Her request: to buy an apartment (about half of it would be savings, another half would be me getting a loan)
She would live in that apartment, but apartment would be on our daughters name.
And finnaly, child would get joint custody, living half of the time with each parent.

I asked for some time to think about that proposal, basically because I am shocked with fast development of situation, and because I am aware that something will come up that I didn't plan for and she took it for granted.

Your help:
any advice how to continue with 180, maybe not everthing is lost
for divorced and separated: what were the situations that surprised you (basically what should I agree on while I can)