Your tomato needs: potting MIX (anything that says "soil" is NOT good for pot/container growing), a bigger pot with bigger drainage holes and more fertilizer - one SPECIFICALLY formulated for tomatoes!
I have grown almost all my tomatoes in various size containers for many years, from a re-purposed waste paper basket to 94.6 liter fabric gro bag. I researched your plant: it is characterized as a micro dwarf, 40 cm tall, producing 2-3 ounce cherry tomatoes that ripen all at the same time.
Potting MIX contains perlite, a non-nutrient extruded rock substance that prevents compaction and improves drainage of the growth media. Potting soil doesn't, leading to compaction, poor drainage and a suffering (if not dead) plant.
I strongly advise a tomato fertilizer, since a tomato has specific macro- and micronutrient needs. I don't know if you use both fertilizers together, but even if so they're starving your plants (which will result in anywhere from a dead plant to poor or no production.
I'm in America and am unfamiliar with what types of fertilizers etc are available to you. Just the macronutrients alone (the NPK = nitrogen-phosphorous-potassium) will not fully support growth. A formulation of 5-10-10 or even 7-7-7 is insufficient UNLESS it also has the micronutrients calcium (Ca for plant growth and prevent blossom end rot - BER- where the bottoms of tomatoes rot), sulfur (S for growth, create proteins and WITHSTAND THE COLD) and magnesium (Mg as the center of the chlorophyll molecule where the plant turns sunlight into energy for itself). Only Ca and Mg can be supplemented.
Some other important micronutrients are:
Zinc (Zn for plant growth)
Boron (B for flowers, pollen viability and fruit ripening)
Last, but not least:
iron (Fe)
copper (Cu)
manganese (Mn)
molybdenum (Mb)
Of course, when tomatoes are grown directly in the ground, the trace amounts needed are almost always available. But when growing in a pot/container. . . it is up to the grower to supply the necessary micronutrients. So mix the fertilizer/supplements into the potting mix BEFORE introducing the plant!
Although you have a micro dwarf, its roots are nearly full size: the size of the new pot needs to be double: at least 24 cm. Only one central drainage hole is required, also doubled in size to 1 cm. Cover the drainage hole (inside the pot) with window screen mesh - to prevent the potting mix from draining out!
Some put their tomatoes outside during the day when its 15.6 Celsius (C) and outside at night when its 10 C. At 4.4 C at night, the plant's growth is stunted and it has wilted leaves. I think I can also see evidence of frostbite on the crispy edges of some leaves.
Those white spots on your soil that turn to powder when touched is indeed either mold or fungus. To prevent, sprinkle the surface with cinnamon (from the kitchen. . . sorry, Mom!) and bottom water using a tray. The plant will use that drainage hole to take up however much it needs. . . in about 26-30 minutes.
Lastly, come on over to the 2023 Tomato Gardening thread, in the Vegetables and Fruit forum. There's alot of us friendly tomato heads, willing to help/advice/support all levels of tomato growers!
Welcome to the fascinating world of gardening!
