Tactics question: How would you play my PC? [custom 3.5]

[bihlbo]

I've been having fits with my character in combat. It seems like most of the time I cast a couple of spells and wonder why I have any others. It would help to get some advice. How would you play this PC?

Level 17, class is "sorcerer-like" but magic is somewhat house-ruled (explained below)
Str 7
Dex 12
Con - (undead)
Int 28 (that's a +9 modifier; Int is my casting ability score)
Wis 15
Cha 16

Fort +5
Ref +6
Will +16
HP 133

BAB as cleric (+11)
AC 19 (+1 Dex, +5 natural, +3 deflection)

Relevant Feats and class features:
Daunting Presence (Libris Mortis)
Empower Spell
Extend Spell
Scribe Scroll
Maximize Spell
Improved Counterspell
Spell Focus (necromancy, total bonus to DC from feats is +3)
* Maximize spells of necromancy school for only +1 spell level.
* Necromancy spells are "cheaper" (see below).
* Concentration skill so high I never fail to cast defensively.

Houserule information about spellcasting:
No Vancian spellcasting. Spell level = spell points required to cast the spell. Spell point pool for this character is 26 (because of the above class feature, necromancy spells "cost" 1 less spell energy, minimum of 1). All spells are cast spontaneously, but metamagic feats do not increase casting time.

Spell list:
Note: an asterisk * means it's a necromancy spell, an M means it qualifies for maximizing. A few spells are from the Spell Compendium, and a couple are renamed for flavor, but the short custom descriptions should make things clear (they have all the calculating done already).

lvl   spell name                 description      

[Korwin]

Polymorph Any Object is so powerful, it might ruin the campaign if you are not careful.

What type of Undead are you?

[woodenbandman]

I'd get craft contingent spell or just cast contingency from a scroll to set off a Harm if you drop too low. Don't wanna get trashed.

Also...

Yeah, cloudkill and bone thicket are pretty much your best combo. You trap all the enemies and you deal loads of CON damage.

[bihlbo]

Polymorph any object uses the PH2 rules, and we have an agreement that it has to be used for dramatic purposes. I don't turn dragons into sheep.

I cannot get craft contingent spell, but a scroll of contingency is a good idea, though quite challenging given the DM and setting. He's a right stingy bastard.

What I hate about cloudkill is this: it's indiscriminate (though being a lich and having undead minions means it doesn't hurt me), it lasts a long time and therefore has a good chance to kill innocents, and I have no control over it at all, making it only truely useful when I control the battle's terrain (or get lucky by finding a bowl). Otherwise yeah, it's excellent.

If I were to add 3 more spells, of the abjuration, transmutation, necromancy, or conjuration schools, what aught they be?