Aether: I'm going to bed shortly, so I can't dig through mantles right now, but yes, you can ignore class skills. If you think it makes sense for your Fighter/Barbarian to take full ranks in Perform (Accordion), go for it.
The feature is actually called "No Time to Think" and it just treats the mental skills as if they have 0 ranks in it, so one could have 3 ranks in craft just if he were to use it to make something no skill points would be added to his roll. As for the character I was hoping the Illumian, and half minotaur would balance each other out into a tall gruff humanoid that would be moderately attractive. I mean he won't be pretty like an elf, and he'll have horns, but devils have horns, and lots of people find them charming. Also with leadership not everyone uses flowery words to lead, and Intimidate is unaffected by No Time to Think. Anyway the only reason I wanted the half minotaur was for the warhulk, so if warhulk is out I'll just make something else.
No Time To Think is very clear. You are considered to have no ranks in intelligence-based skills. So, for qualifying for Exotic Weapon Master, you are considered to have zero ranks in craft and thus cannot get in. However, War Hulk is out either way.
And I don't require elf-beautiful (I don't even like elves all that much), but... there's a limit. War Hulk is past it.
Do note that all you've given me so far is "Giant brute with a neon sign over his head," which is really worrying without additional qualification and explanation as to what the Hell this thing is beyond those numbers.
Artificer is treated as 2 higher (mostly; check the limitations in the class), so a 10th-level Artificer could make a 12th-level ability.
However, the CL of a piece of equipment is equal to three times its effective
enhancement bonus. A +3 enhancement with moderate fortification (a +3 ability) comes out to +6, which requires a CL of 18.
Also, if you want to make what is effectively a +6 suit of mithral armor, you're not actually
making a +6 suit of mithral armor. You're taking a preexisting suit of masterwork mithral armor (the price of which is outside of your benefits, unless you make it yourself, in which case it would be a separate nonmagical item), then enchanting it with your +6-equivalent enchantments (which you can't actually pull off just yet, you're limited to +4-equivalent for now, but moving on...)
So, the market price of the enchantment would be 36,000gp. Halve that for making it yourself, for 18,000 gp.
However, it sounds like you're using both Magical Artisan and Extraordinary (or whatever the gp one is) Artisan. If that's the case, I can't allow that, since it's stacking the same effect across settings. If it's something else, lemme know.
As for how cost reductions stack? Two -25% reductions would not be -50%. 25% off of 18k is 13500. 25% off 13500 is 10125gp, on top of whatever the physical armor itself cost.
For XP, 18k/25 is 720 XP. 25% off that is 540. That can come out of craft points, but as a houserule, I'm not letting XP be treated as a currency; instead, you pay five times the remainder in gp (your other gp reductions don't apply). So, if you spent 200 craft points, there'd be 340 XP left, which becomes 1700 gp, which you add to your 10125 gp plus whatever the original armor cost.