A:  There is a dilemna here.  Murphy's Law would state that "Only If You Don't Have A Spare Battery Will You Ever Need It".

My advice...carry a fully charged spare (at least one).  When the battery in your camera shows 'low' replace it with your spare and charge the battery that you just removed from your camera.  After charging put it back into your bag as the spare.

If your camera uses AA batteries or some other commercially available battery feel fortunate.  Try to purchase re-chargeables but feel comfortable that perhaps anywhere in the world you'll be able to purchase batteries from a store.

A:  Well, the spots could be several things.  How old are you?  Just kidding!
If you have a DSLR (Digital SLR) it is most likely that you have dust on your sensor.  Camera manufacturers are trying to engineer "dust on the sensor" out of the picture...but the reality is that when we take a lens off a camera, or operate a large zoom lens (which acts like a bellows) dust gets into the sensor chamber and some of it stays on the sensor...which causes spots on images.  Here is a link to an article about removing dust

Personally, I hate sensor dust and have learned to be very careful about changing my lens. 

A:  I teach that a photographers should shoot .jpeg, highest resolution (use all your pixels) and highest quality (least .jpeg compression) for the following reasons:

1. Murphy's Law states that if you shoot at less than your full capability you will capture your best image.
2. You cannot see the future (nor can I).  However I know that there will be more capability in the future to do more with images than there is today.  If you capture your best images today you will have a better opportunity tomorrow to do even more with them.

Rules are made to be broken...and RAW is made to use.  Stay on the learning curve.  Keep challenging yourself.  Do your best!