PF Stormborn DC

[Perseus]

So I'm currently making a Stormborn Sorcerer for a PF game.

Since mundane classes have all the weaknesses of 3.5 I figured a caster should do nicely.

I don't want to go overboard on the damage but I would like to get reliable damage. If I cast Lightning bolt, I would like that the DC be as high as it can be. Because of this, I won't be taking any metamagic other than heighten spell and elemental spell (doesn't change the descriptor). No traits will be used.

For class/feats relating to DC have...

Class: +1 (W/electricity descriptor)
Spell Focus: +1(evocation)
Greater Spell Focus: +1 (evocation)
Elemental Focus: +1(electricity)
Greater Elemental Focus: +1(electricity)
Heighten Spell: higher spell slot = higher DC
Elemental Spell: Change damage (not descriptor) to Acid.

So at the end of the day I have a base DC equal to 10 + 3 (cha... Rolled horribly... But it is a 17) + spell level + heighten spell + 5 = 18 + spell level + heighten spell = x

So lightning bolt (3rd level) DC is 21 + heighten spell.

Is there any other ways to boost my DC? Again i'm not looking to boost damage, just the rate at which damage occurs.