Something else we noticed, Combat Casting Feat. Do you need it?
It turns out in this build, I don't.
Looking at him at 5th level now...
INT 20 (+5)
Focused Mind Trait (+2)
Level 5 (+5)
Improved Bonded Item (+2)
Concentration Total 14
He can only cast 1st and 2nd level spells anyhow.
Level 1 DC 17 (Fail 1-2)
Level 2 DC 19 (Fail 1-4)
Sure Combat Casting would make these never fail, but the chance seems not worth spending a feat. And if you really need to, you can just take a hit to attack rolls for a boost in Concentration for that critical spell that HAS to work.
Then come 8th level you get Improved Spell Combat for +2 more Concentration so you look like this:
INT 20 (+5)
Focused Mind Trait (+2)
Level 8 (+8)
Improved Bonded Item (+2)
Improved Spell Combat (+2)
Concentration Total 19
You can actually cast 3rd level spells at this point and have been able to.
Level 1 DC 17 (Auto Success)
Level 2 DC 19 (Auto Success)
Level 3 DC 21 Fail on a 1!
It stays pretty nice from here on out.
So for my Magus, no Combat Casting!