Armor: get Celestial Armor made of Mithril, that will allow you to have a +10 Max Dex bonus (some DMs allow it, some don't, from what I have read, it is allowed). Mithril Celestial armor increases Max Dex by +8, and decreases ASF by 25%, so a Mithril Celestial Breastplate has a Max Dex of +11, no ACP and no ASF, allowing you to continue bumping up your dex into the stratesphere(32).
Drop your strength and beef up your Con or Int or maybe your charisma if you like. Drop Two-Weapon Fighting...hard to cast spells with both of your hands full. To cast you would either have drop the weapon (free action) or sheath the weapon (move action, unless you plan on taking quick draw later) because you can't hold two weapons in one hand to cast. Replace with Weapon Finesse, and invest 2 skill points in perform (dance). Take Dervish Dance http://www.archivesofnethys.com/feats.htm#dervish-dance . Now your Dexterity is used for attacks with the Bow, and attacks and damage with your scimitar. In addition, this leaves one hand free so you can cast your spells.
You are also missing Deadly Aim, which is a huge boon. After you get Dervish Dance, an investment in Power Attack will net you a nice healthy damage increase as well.
Two-weapon fighting is really, really hard in pathfinder to make work. It requires a huge investment in feats, for a small return, that (damage wise) can be made up with power attack. The only class that TWF is really a powerful ability for is melee rogues, who can dish out sneak attack damage on flanking attacks. Considering you are a bowman who likes to cast spells, swordplay is not going to be your forte. If anything it is going to be 4th on the list after mitigation/defense.
Without a breakdown of classes you have taken, I am assuming you went with 4 fighter and 2 wizard? in order to qualify for AA, so you really aren't too focused on casting...per say. I would snag one more level as fighter to get the Weapon Training +1atk/dam with your bow, then take 3 levels of AA, and then round out with all 10 from Eldritch Knight.
As for other magic items, your best defense, is going to be to stay away, so you can use your awesome bow attack of doom, so I would concentrate on flight items (or a quickened metamagic rod to cast fly as a swift on the first round of combat, then the move action to fly into position). Proper aerial position will remove the penalty for soft cover provided to the monster from your allies, and precise shot negates the combat penalty, giving you no negatives on your attack...that is just gravy. Bracers of Archery are nice, they will partially pay for your use of Deadly Aim.
Lastly, if your mean Arcane Archer by AA (I am assuming this), the fact that Archer is in his name, means that he is NOT primarily melee.
Lastly, if your mean Arcane Archer by AA (I am assuming this), the fact that Archer is in his name, means that he is NOT primarily melee
Hello, my name is Laurefindel and I'm an alc... oops, wrong kind of AA!
Well if you max level is 12, and you spend them F6/W1/AA5 you will have a caster level of 4 (2nd level spells), BAB of 11. If you spend them F5/W2/AA5, you will have a caster level of 5 (3rd level spells) and a BAB of 11. So, do you want a feat....or third level spells (3rd level is one of the best level of spells..tons of goodies to be had there).
Now I understand where you are going. hmm. If you go with 3rd level spells, and use flight for positioning...you really shouldn't need a lot of AC from armor, you'll be better served by AC from Dex/Deflection/Dodge (I forsee many casters launching ranged touch attacks at you...at least, I'd do that to you if I were your DM). So, I would at least go for Celestial Armor from Core...its only like 23k, and gives a +8 Max Dex, and one use of flight per day.
An alternate build:
F4/W2/HW3/AA3
Take the Plane of Air for Terrain Mastery and Terrain Dominance, and you can fly (as per the spell) 3+Wis/day. Not to mention all the other goodies it has with it. This combo would have Caster Level 4, BAB+11, so it is about as optimal as your current build...only you can fly... 5 times per day (3 + 1(Wis) + 1(armor)), which should be enough to last you most of the encounters.
I still contend that your best means of mitigation is going to be distance.