The Tropical Fruit Forum

Add gypsum and use epsom salt. Bring down your soil pH. Probably your rootstock is Gomera type, which can take some salts well but your pH is still high.
Why would you spray calcium nitrate of course will burn all new leaves.

The tree was undercover and heated probably with a heating cable that means it had a microclimate, then it should survive. To be truly cold hardy should be expose directly to that temperature.

Coffee arabica nana is a dwarf cultivar for pots, you should try that instead of regular coffee plants

Following few techniques and cultural practices I managed to induce a massive flowering this year on my small satsuma 'Okitsu' mandarin. I hope I will stop the fruit drop and have a  mandarin for every 4 leaves.

https://www.youtube.com/watch?v=pqXJRYXjlRQ
https://fb.watch/5MxmxcGq8l/

Yes, musa Velutina

Bees will do the work. Just watch out different types flower at different times depending on the climate. So you can end up with A flowering but no B flowering. So things get complicated.

New growth gets damaged.  I can't see any insects.
Is this from spidermites or some fungal problem?

Check this September with me, I might have some seeds.

I have 5 avocado varieties. I keep them in small pots from 15 L to 50 L, they all flower now.
Last year they set fruit but I cut them because the trees are young.
I keep my trees outdoors from last frost to first frost. Then during the winter in as basement or a cold room at 2-10C for 3 months. None died, they do well in cold.

I don't think one needs 200 L container. In Japan they grow it in 70L and get it full of fruits.
I believe your problem is the lack of varieties A and B. And the flowering period. Here they flower now.

I found in a shop a couple of organic lemons packed with a small twig and a couple of leaves. I couldn't   missed it, so I graft it on citrumelo.

Lemons are juicy and acid, with a good balance. These are from Italy from La Costiera.

Product description
Biological Primo Fiore lemon is a citrus fruit that has an elliptic form and middle sizes, it presents a light yellow peel very thin and a juice of high acidity.
Lemon Primo Fiore differs from the other citrus fruit for a very intense taste for the presence of high acidity in the pulp and for the abundant juice. The peel is light yellow color, of middle thickness, fine grained, while the maturation of the fruit begins at the end of October and is extended into the first days of April. It presents a middle-big size, it differs for the color, for the thin peel and for the high content of citric acid.

I would provide shadow for the tree, with 60% shadow fabric. A root biostimulator would help with amino acids.
If the trunk is split I would seal it all in parafilm and paint it white.
The new growth came out when the sun is already too strong and the plant can't adapt.
To grow new roots you need foliage to provide sugars so if the new growth dies the tree might die.

Citrus grows very well with high humidity. I mist my plants every day in gh.

You would probably need to trim the roots and the top every 2 years, so some years you will not have full fruit production. I do it this way, a lot of work though. Flying dragon will take 10 years to fill that pot