but would leave you without a free hand to cast with. The other hand has to hold a weapon.
Rods also count as maces I think.
only certain ones, its specified in their description. No metamagic rods are.
Do what your DM was too immature to do- and talk about it with him.
Changing your damage type is just going to cause all the creatures to grow brand new immunities. You need to talk to him rather than try to alter your character.
This is something he should have done (talk to you) rather than to alter the campaign world to "fix" a character he perceives as overpowered.
-S
You could dip one level of crossblooded sorcerer and take one of the bloodlines that lets you change the damage type of spells. You could also get a second bloodline like orc to buff your spell damage. This is probably not what you want if you weren't interested in spending a feat...
Also, if you talk to your DM, find out if he considers you too powerful. Suggest that they simply have lightning resistance, instead of immunity. Or make only some enemies immune to electricity, forcing you to make knowledge checks to try to identify weaker targets