3 Diffrent sourses on the web say 3 diffrent things, base is NaOH btw
1 says base to ph7
2 say base to ph10
3 say base to ph 12

so which of them is correct? anyway with dcm extract at ph 7 its bears unbreakable emultion for now..

is too much base can decompost the alkaloids?

Most aliphatic Amines are freebased around ~ 9,5. Here is a picture for Bufotenine - it has many protonation variations, the one that would be equivalent is H-SR (equals H-Mesc).

You can see that equilibrium (pKb) is at 10 but you would need 12 to freebase 100 %. So I guess pH 12 also should freebase 100 %, while at 10 it might be not fully H-Mesc. But then I have no clue about cacti ...