I am at level 13 right now and I can easily buff my fortitude to 145 with Stalwart resting bonus which provides +2 might and +2 constitution and food bonus. That would be 155 against petrifying if stacked with Body Control.
I still have 1 or 2 quests left that can buff my MIG or CON, and just think about level bonus and the POE edition of Crom Faeyr which gives another +4 MIG...OMG it's unbelievable...that would be at least 170?
How could I ever be petrified or stunned with fortitude like this? I don't even need scrolls or potions!
And I took the 30-pt shield Chant at level 13, made a custom chant that combines shield and Dragon Thrashed, and that's ridiculous! Though I haven't tested it on difficult enemies I think it would make a difference...
Chanter is really OP...perhaps I should try something harder on my next play through lol