Harmony - Troop Symmetry

By the way, is it possible to do this without any consequences and without modifying the executable file?

It is possible, but for that, you will have to delve into the scripts and learn the Lua programming language, at least to some extent.

But I don't need to increase the damage, I need to increase the amount of health.

No one will even touch a ballista with low damage; what's the point of increasing its health? And the damage will be low due to the inability to simultaneously upgrade both ranged attack and multi-shot.

and the number of resurrections at the tent (the number of times, not the strength)

An upgraded tent is already a great help in clearing out enemies, allowing you to resurrect 1-2 tier 7 creatures (3 x 100 hit points) for each battle. Even if you have only 1 difficult battle per day, it effectively provides an increase of +10 dragons (for example) per week for free by replenishing losses. Resurrection itself is many times more important than damage of the same amount when it comes to clearing out enemies with losses.