I think steppers are not really efficient motors so i doubt its the type to run from a battery, but on the other hand i suppose you do not have much choice. For a mod, if you run it only full step (no microstep), its likely to get just a little better efficiency than in microstep mode. And if ran in full step, better go with 0.9 angle motors and try get some resolution increase with bigger gear ratio instead. Well, anyway this is just an opinion.
Steppers do run kind of hot in the usual manner. Hard to say which kind of hot is too hot. If you can keep your finger on it, that should be normal-ish.
About not equal steps i dont see a video in your post but here try check this out perhaps its informative.
If you try the driver with a3977 also mentioned in that post, that driver might provide more tweaks and hence my accommodate your motor(s) better. You could find it on reprap page as "stepper driver v3.3". But i dont think they are making this chip in plcc anymore, maybe you find some on stock or perhaps better as a3979 in plcc which is pin compatible and 16x instead of 8x. Good luck.
Steppers do run kind of hot in the usual manner. Hard to say which kind of hot is too hot. If you can keep your finger on it, that should be normal-ish.
About not equal steps i dont see a video in your post but here try check this out perhaps its informative.
If you try the driver with a3977 also mentioned in that post, that driver might provide more tweaks and hence my accommodate your motor(s) better. You could find it on reprap page as "stepper driver v3.3". But i dont think they are making this chip in plcc anymore, maybe you find some on stock or perhaps better as a3979 in plcc which is pin compatible and 16x instead of 8x. Good luck.