Thanks for the help, folks!
I hadn't thought of leaving spots open for utility. Would that prevent spontaneous casting? That is, can I convert an open slot to an inflict spell, or do I need to fill it with an actual spell first?
Divine favour is of very limited use because it specifies weapon damage, so it doesn't help with eldritch blast.
Deathwatch is a decent idea that I had somehow totally overlooked. I guess I'm so used to playing Good PCs, I developed the habit of ignoring [Evil] spells. This character is LE, so he can cast it without trouble, and it would help pick out vulnerable targets for his Death domain power.
Nail, you're probably right about dropping the cleric level. I'm reluctant to go there due to RP reasons, but it might be necessary for the good of the party. We're in the front end of a notoriously difficult module (*cough*Hommlet!*cough*), so if I want the character to survive, I may have to drop my RP snobbery and make with the powergaming.