Hi,
Aren't you making a mistake: you are calculating how Constitution (an therefore, Vitality) changes when changing The Constitution points a Character has, but for ONE Single level. But Constitution grows with the character Level, so it would be more useful to have the formula for the constitution as a function of player level. I don't see how you can derive this by using a single character level in your calculations.
This page mentions the following about "Constitution" in Divinity: Original Sin Enhanced Edition
https://divinity.fandom.com/wiki/Attributes_(Divinity:_Original_Sin_Enhanced_Edition)
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Constitution
1 Maximum Action Points per point
6.2 Vitality per point and level (+7.13 in normal difficulty due to the +15% bonus)
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