1.) Don't try to pick all acid spells. Pick up the energy substitution feat to modify your spells.
2.) That's really a matter of preference. While wizards do have to re-memorize spells, they also get those meta-magic bonus feats which can help a bunch.
That depends heavily on what you are really trying to accomplish. For instance, are you hitting the acid theme hot and heavy? Are you willing to pick sub-optimal spells to stick with the theme?
I would, presuming that the character theme is most important to you, go with sorcerer. They are the ultimate in artillery platforms and that is what you seem to desire... not to mention my own personal preference
I would also try and find spells that require ranged touch attacks and pick up ranged spell specialization and the other feats that deal with ranged touch, such as weapon focus... I think. Energy Substitution is also a good feat to pick up. Later!
I second (or third?) the suggestion about taking Energy Substitution as soon as possible. While the Acid Orb is nice, I'd take Electric Orb (or any other) and sub Acid just for the flexibility. Then there's things like Acid substituted in Fireball, Ice Storm, Lightning Bolt, etc. Only take an Acid spell when you have no other similar spell to learn, like Melf's Acid Arrow.
If you DO go Wizard, make your PC a specialist to get the extra spell and the learning bonus.
Sorcerer, while having less spells known and a slightly slower progression, at least allows you to substitute Acid on the fly.
Multiclassing early with a Cleric will open up other spells to such a PC, assuming the right Domains are chosen, and you follow up with Mystic Theurge so you can advance as both an arcane and divine spellcaster simultaneously. As I recall, the Air, Fire, Sun, and Water domains all contain spells that arcane spellcasters can't use that would still be usable with Energy Substitution.
But..uh...don't forget the obvious: take lots of levels in Alchemy so you can make your own, non-magical acid grenades.
Which reminds me...might an Artificer be a good choice? I'm not 100% up to speed on the class, but from what I understand, their infusions work pretty much like spells, and you can have a bunch of stuff prepped for use- possibly in unusual forms.
If you want to go all out acid, Elemental Savant, Earth (Complete arcane) would be the best choice. It causes all spells with an energy desciriptor to do acid damage, it also gives you defences and bonuses with it.
Why spend a feat on Substitution when you could just research an acid version of a normal spell? As long as you have an even remotely fair GM he should let you pick Acidball instead of Fireball without too much of a fuss.
Why spend a feat on Substitution when you could just research an acid version of a normal spell? As long as you have an even remotely fair GM he should let you pick Acidball instead of Fireball without too much of a fuss.DS
Because memorizing only acid spells limits the flexibility of your spellcasting. Without the feat, if you run into something with an acid resistance or immunity you've just lost half your spell arsenal. With the feat, you always have a choice of using the spell as written or changing it to acid.