I cannot suggest Silent Spell enough for you. I know my GM loves to toss things that cast Silence at me to get me to shut up. Even cast it area effect to bypass the whole will save thing. Sure, you are casting at +1 CL, but at least you can still cast.
Also, you want to get those Charm spells off easier? Invisibility + Silent Spell. Your targets never even knew a spell had been cast at them.
Heighten Spell simply lets you blow higher level slots for a higher DC on the resist. This is how you bag a BBEG with a Charm, even at higher levels.
Extend Spell is probably not too useful for you, it only doubles the duration. Generally, that is not an issue.
Reach Spell might be valuable to you if you want to cast all those touch spells at a range of 30'. Pretty handy to combo with Chain Spell for group-buffing
Speaking of Chain Spell, it's an extremely handy spell. Basically, you not only hit primary targets, you ALSO get secondary targets. So Charm Person + Chain Spell = Mass Charm Person. This can help you free up some useful spells known slots at higher levels. Oh, and Chain Spell + Greater Magic Weapon = millions of gold in savings on only getting +1 weapons of x, y, and z while swinging as +5 weapons of the above enhancements.
Persist Spell is a bugger. On the one hand, a personal spell now has a duration of 24 hours. Like Mirror Image. On the other hand, +6 CL bites. Now, you can Thesis this to make it less painful, and there is another feat which reduces the cost of a specific metamagic feat by one (minimum of +1) that you can also apply to Persist to take some sting out as well. However, it is very potent.
Now here is the cheeze that goes with Persist that you should probably consider avoiding: It also works with spells that have a fixed range. Like, say, a spell which you Reached for a fixed range of 30'. So you can persist a Reach Invisibility onto an ally, who will remain invisible until he attacks. With Thesis and the feat which specifically reduces the cost of a metamagic feat by +1 (minimum +1), you can actually Persist a Reach Greater Invisibility. Then Chain it. For the entire party being invisible for the whole day. Even after attacking. Yea, that's crack, and I wouldn't suggest doing it. However, normal uses of Persist is to make your rounds/level self-buffs last all day long, and is perfectly usable.