Blunting Field requires 'base' M. Protection...

So somehow you kind of need 800 Intelligence to raise your 'base' M.Prot to 40?

I wonder if catering works if it's not base stats, but is a buff stat.

800 Int is very easy to obtain compared to the other stats, so a Catering is excessive. However, a Catering should work, as long as it grants Bonus Int. The Bonus Int will contribute to Base M.Prot.

Stats from Equipment also count towards "base" stats.

Like there's no way to get "base" regular Protection, but wear some armor or some accessories that have Prot on them and that'll activate Blunting Field. It works the same way with M. Prot. So wearing M. Prot-boosting armor can help as well as Catering. In this case "base" doesn't mean "natural".

Yeah it has to apply to the Bracket in the respective stat that is being checked. Though checking the gear, guard cylinder adds magic prot, it increases the base as well as the 'current'... Which is weird.

So Gear based stats and buffs applies, but skill based stuff does not.