So, yesterday over a glass of wine, I discussed your case with the notary in the family. (Since I am NOT a lawyer and may not be able to provide complete information, this is NOT legal advice)
1) Usufruct rights on houses without land are very difficult - because in the case of renting out, you would have to assign a part (how much, how value increases are considered) of the rent to the landowner.
2) A right of residence for you would probably work, it could be contractually regulated which part of the land you are allowed to use and that the right of residence remains valid even in case of "not living there" (so you can move out and the house then remains empty, cannot be used otherwise).
3) In the event of inheritance, the value of the house would be deducted from the estate if you can prove beyond doubt that you paid for the house. But only the economic current value of the house would be deducted (-2% per year). That means if you inherited 20 years after the house was built, 60% of your original construction costs would be deducted from the estate. In times of rising real estate prices, this is rather disadvantageous for you.
It would make sense to divide now and have your share gifted to you by the parents. The house value would then also be deducted at current value, as in the case of inheritance. It costs a few thousand euros but then the situation is clear.
With the re-survey you might even be able to achieve that the adjacent land (which apparently the municipality wants) is merged with the other properties (in other words, making 2 from 2 but with different dimensions).