Dragon Shaman Build?

[JeminiZero]

So. I was thinking to myself: how do I optimize a Dragon Shaman? And after a bit of research, I came up with this:

Human Dragonborn Copper Dragon Shaman

Shamanic Invocation Alternate Class Feature: Lose 1 Draconic Aura, gain 1 least Dragonfire Adept Invocation. Probably lose the Presence aura (bonus to convo skills) for See the Unseen (for darkvision and see invisible).

Probable 32 pt buy stats:
2 Str 10
10 Dex 16 -2 Dragon Born = 14
8 Con 15 +2 Dragon Born = 17
6 Int 14
0 Wis 8
6 Cha 14

All level up points go to Con to bring it to 22 at level 20.

Feats:
1. Able Learner
3. Recover Breath
6. Entangling Breath
9. Shape Breath
12. Double Draconic Aura
15. Endurance OR Force of Personality???
18. Steadfast Determination OR Clinging Breath??

So the idea is that by level 4 you can alternate between Dragon Shaman and Dragonborn breath weapons as your primary offence, and all your subsequent breath feats apply to both. Use Entangling breath as necessary to debuff, and combined with Energy Resistance Aura, lets you use your breath weapon with Allies in the area, without damaging them (as Entangling breath halves breath damage, which the energy resistance can cover).

In the face of large number of weak enemies, you can use Shape breath to crank out for 50/60ft cones by level 10, and 100/120ft cones by level 20. Copper Dragon lets you spider walk your way round obstacles/out of trouble, and later on share adaptation lets you spiderwalk your whole party around. Finally, Human with Able learner and a decent Int score lets max Bluff (Copper Dragon class skill) and you can crank up useful CC skills, like UMD, Spot, Sense Motive, Disguise Self.

I am having problems trying to figure out the last 2 feats (3 feats if you think Able Learner can be dropped for something more useful). At present I have 2 feat sets:

1st set uses Endurance and Steadfast Determination let it apply its high Con score to Will saves.

2nd set uses Force of personality for Cha to will saves, and Clinging Breath to try and beef up the damage output a little against single strong enemies.

Is there any other feat or sets of feats that can serious up the damage output on breath weapons? As it stands, (I think) it does good damage from 1-5, ok damage from 6-10, and then is quickly outpaced by Power Leap Attacking Shock Troopers (PLAST), and of course Wizards and CoDzillas. Is there anything I have not thought of that can improve this build?

[Signmaker]

Well, you ARE a dragon shaman, that DOES have intimidate as a class skill, and it's not TOO hard to beef it up...

Frightful Prescence.
Intimidating Strike.
Possibly Nymph's Kiss to replace Able Learner. Gives you sommoar skill points, and charisma-based skill check bonus, and a bit more to your saves versus spells.

Circlet of Persuasion, Max Ranks, have fun with your menacing shaman.