I am quite sure that Keraji and most probably early Satsumas are the long term hardy in your area.
But for this they should be high grafted ( more that 50 cm) on poncirus rootstock , preferably grown in situ to preserve a long taproot.
I might try grafting onto TaiTri, when the seedlings eventually get bigger.
I'm pretty sure Satsuma is marginal here, the one I have that was covered is grafted onto dwarf rootstock so I'm pretty sure that's poncirus.
The Keraji seedlings were both grown from seed and on their own roots, obviously.
Admittingly the Satsuma wasn't the biggest or mature, and the Keraji seedlings were certainly small seedlings, but part of that is demonstratrative of the lack of growth from the short growing season in this climate.
Ilya, I believe the climate here is quite similar to France, although a bit more continental, the summers can sometimes get very hot, and the Winters, although for the most part relatively mild, can sometimes have bouts of snow and an occasional sudden temperature drop over the night. This Winter was a bit unusual. Most years the snow doesn't stick to the ground very often, but this year was virtually a snow storm for a week. Branches in the trees broke from all the snow.
Tonight, by the way, is the last night temperatures will dip below the freezing point this year.
Actually, I'm looking at the temperatures right now and it looks like France is just a tiny bit warmer than here this week. The temperatures are a bit more unstable here. Part of that may be because it has been fairly dry here and where you are it's been getting a lot of rain. (Rain releases heat as the water vapor condenses, so rainy days in the cold season will not be quite as cold)