I have been away from the board for a while and have just had a catch up on your situation.
One thing that comes across in your posts, is how similar of a pattern these stages and interactions are after a breakup.
I could have used the words you are using myself.
So as someone who threw themselves into this process not so long ago myself, and was able to improve my life - which led to my wife returning.. I offer you this advice.
I have spoken many times to my wife about certain things we spoke about when she left. Such as, when she sent a message with a heart on or called me a pet name for example. For me at the time it was something to hang onto. In truth, by her own admission, romantically she was done for a months before she left, and her actions where to make the split easier by being smiley and friendly and saying she still loved me etc.. but in the end the outcome is same. Its over. And we convince ourselves it isn't.
Please do not read into every situation. Which it seems from your posts that is what you are doing. She is being nice to you and using pet names, more than likely because she feels guilty because she loves you. But in the long run the aim is let you down gradually.
Your nicely worded messages of thanks are pleasant at best, but will not have any bearing on the outcome of this situation.
The only thing that is going put you in the general direction of potentially resolving this situation is you stopping interacting with her in this manner, and to truly accept that some of your behaviour is to entice a reaction from her.
i.e. telling her you have learned a lot from the trip.. if you are honest with yourself - telling her that, is your true message of ... i have changed.
You hope she will think.. Maybe Davide has changed, maybe it can be different this time?
I understand how hard this is. The reason I am spending 30 mins of my time typing this is because (despite how unique you think your love with your wife was) its no different to 90% of the rest of us here.
At the end of all this I have no doubt things will be good for you - but at the moment despite your best efforts, I would advise to stop doing anything that is used either consciously or subconsciously to get a reaction from your wife.
