Attack Routine
Dual-wielding two bastard swords with Two-Weapon Fighting and Exotic Weapon Proficiency (Bastard Swords) causes you to take a −4 penalty for wielding two one-handed weapons. If you were to wield a one-handed weapon in one hand and a light weapon in the other, you’d have only a −2 penalty.
In addition to these penalties, you have BAB +7/+2 (that is, two attacks, one at +7 and the other at +2), and a +4 Strength modifier. As a Fighter, you have Weapon Training, which is a +1 to attack and damage as long as you use weapons from the chosen group (which is another problem because you have to pick between Heavy Blades and Light Blades).
So as it currently stands (with the −4 penalty), your attack routine is this:
Dual-wielding Bastard Swords, Heavy Blade Weapon Training
Bastard Sword +8, 1d10+5 (10.5)
other Bastard Sword +8, 1d10+3 (8.5)
Bastard Sword +3, 1d10+5 (10.5)
If you had a bastard sword and a short sword, you’d instead have a −2 penalty, like so, but you’ll only get Heavy Blade Weapon Training on the Bastard Sword attacks
Bastard Sword and Short Sword, Heavy Blade Weapon Training
Bastard Sword +10, 1d10+5 (10.5)
Short Sword +9, 1d6+2 (5.5)
Bastard Sword +5, 1d10+5 (10.5)
You lose an average of 2 damage on the second attack, but you are far more likely to hit with all three attacks.
If you swapped the Bastard Sword for a Longsword, saving yourself a feat, you would have
Longsword and Short Sword (+1 feat), Heavy Blade Weapon Training
Longsword +10, 1d8+5 (10.5)
Short Sword +9, 1d6+2 (5.5)
Longsword +5, 1d8+5 (10.5)
On average, you lose 1 damage from each of your first and third attacks (2 damage less total), but you have another feat which may be able to give you more damage than that. A really simple example is to switch to purely Short Swords, and take Weapon Focus and Weapon Specialization with them. This also allows the Light Blade Weapon Training to get the bonuses on all of the attacks.
Dual-wielding Short Swords, Weapon Focus and Weapon Specialization (−1 feat), Light Blade Weapon Training
Short Sword A +11, 1d6+7 (10.5)
Short Sword B +11, 1d6+5 (8.5)
Short Sword A +6, 1d6+7 (10.5)
Note that this version has the highest attack bonuses and the same damage potential as the two bastard swords. Weapon Focus and Weapon Specialization are not exactly high-power feats, but they’re better here than Exotic Weapon Proficiency in the Bastard Sword. (to be fair, I used two feats to do it, but Weapon Focus in Bastard Swords doesn’t really help much since either you’re taking huge penalties for using two or you’re only getting the bonus on two out of three attacks)
Alternatively, you could consider Improved Two-Weapon Fighting, either with Exotic Weapon Proficiency in Bastard Swords:
Bastard Sword and Short Sword, Improved Two-Weapon Fighting (−1 feat), Heavy Blade Weapon Training
Bastard Sword +10, 1d10+5 (10.5)
Short Sword +9, 1d6+2 (5.5)
Bastard Sword +5, 1d10+5 (10.5)
Short Sword +4, 1d6+2 (5.5)
Or with Weapon Focus (Short Sword)
Dual-wielding Short Swords, Improved Two-Weapon Fighting and Weapon Focus, Light Blade Weapon Training
Short Sword A +11, 1d6+5 (8.5)
Short Sword B +11, 1d6+3 (6.5)
Short Sword A +6, 1d6+5 (8.5)
Short Sword B +6, 1d6+3 (6.5)
Note that in the second case, you average 2 damage less on half your attacks, but have +1 on all attacks.
There are still better things you could probably do, these are just some simple, Core feat choices that you should consider without changing your existing feats too much.
Combat Maneuver Bonus/Defense
CMB = BAB + Str + size_bonus + misc
You don’t have a size bonus if you’re Medium (like Humans generally are), so ignore that. The Fighter’s Weapon Training also gives you a +1 as long as you’re using the right weapon, so +1 for that. Your BAB is +7 and your Strength modifier is +2, so your CMB is +10.
CMD = BAB + Str + Dex + size_bonus + misc
Again, size and misc don’t come into play. Weapon Training only helps against Disarm or Sunder, so I won’t include in the general number. So you have +7 + 2 + 2 = +11.
Best Answer
Animal companions with an intelligence < 3 have a rather small list of feats to choose from, as stated here. Given the fact that your T-Rex is strength based, then the feats that come to mind are Power Attack and Improved Natural Attack.
At level 7, Power Attack would let your T-Rex take a -2 penalty on attack rolls to gain a +6 bonus on damage rolls. (I would rule a +8, because of Powerful Bite, but since this is PFS, it's best to settle for Rules As Written.) This penalty can be turned on or off, so if you find you're having a particularly hard time scoring a hit, you can turn off Power Attack to deal normal damage without the attack penalty.
It is important to note that the bonuses from power attack scale as you level up, but they shouldn't change until you reach level 13.
At level 7, improved natural attack would permanently bump up your T-Rex's bite damage dice to a staggering 3d6. This is a passive ability that has no drawbacks, so if you have to pick just one feat, I would recommend Improved Natural Attack over Power Attack. (Unless you've been eyeing bull rush or overrun combat maneuvers, because Power Attack is needed to qualify for those feats.)
You can read the particulars about these feats here:
Power Attack
Improved Natural Attack
Edit: Sorry, I didn't see that your T-Rex's Intelligence is 3, I dug a bit and it seemed that most of the good feats required way more than 3 feats to build for, but I found a few that could also work for your T-Rex:
Blood Feast, A +1 attack and damage after your first hit with your bite attack.
Cleave, You can gobble up 2 foes at once by taking a -2 to AC. Requires Power Attack.
Great Cleave, Only useful for mowing down the mooks, you can use cleave on as many enemies you can reach. Requires Cleave and Power attack.
Furious Focus, You no longer take the penalties from Power Attack on the first attack you make every turn! Requires Power Attack.
Improved Sunder, You can chew up your foes weapons and armor, leaving them squishy and vulnerable. Requires Power Attack.
I would recommend Furious Focus, unless you want to avoid Power Attack, then the only other damage feat I could find was Blood Feast. It is important to note that your T-Rex can't take Vital Strike until level 9.