Just going on a hunch here... so bear with me, pls.
You want to take fighter dip to get light armor proficiency? Why not go twilight mithral chain shirt? Yes, you are not proficient with it, but, that armor has 0 ACP and 0 ASF, so you loose nothing. And it is lighter than breastplate and only 1 AC behind breastplate. Cheaper too.
Now, I would strongly suggest you go Psion 7. But if you really want to dip into something, go sorcerer. It is every kobold dream class. Now, what would you get out of it?
First, you add Loredrake template. Now you are lvl 1 character AND lvl 3 sorcerer. Then you go 5 levels of psion. On 6th level, you get Draconic reservoir feat. Do the greater ritual at lvl 6. Now you should be lvl 4 sorcerer, and 5th level psion. On level 6.
Now, what you get is 1 2nd level spell known, which you can cast 3/day (4 if you have CHA 14). The fun thing is if you get 1 more level of sorcerer (and you were going to dip two levels of fighter anyway), you get second 2nd level spell. Strong spell options are Wings of cover and Alter self (shadow wyrmling gives flight speed 120, and Nat AC 7 IIRC).
And you wear chain shirt without penalties.
As for spear, as already pointed out, it is a very bad idea... you should be dumping STR anyway, and spear would be very weak. Grab instead a light crossbow. Who needs reach when you have range? Same damage, and DEX based which should fit you better. And don't worry about iterative attacks. By the time you get 2nd attack, you will be little mean killing machine using your psion awesomeness. Or should I say koboldness ^^