DSLR vs Point and shoot

Hi all, I'm probably going to buy a new camera sometime this year so I'm starting my research now (I need to research everything to death before I buy). I'm a beginner and I don't even understand what focal point is and all that stuff. Right now I have a crappy Kodak and I can't stand it cause it sucks in medium light settings. even though I have the flash on, the pics come out dark. i'm trying to decide if I should get a DSLR or a good point and shoot. I have some questions about DSLR.

1. why are their optical zoom so low? if you can get upto 35x optical zoom on a good P&S camera (like canon SX40HS, or even some smaller ones) why can't you get it on a DSLR without having to buy a zoom lense?

2. one of the reasons I may want a DSLR is because they are supposed to take better pics than a P&S. will I notice the difference? and will it take significantly better pics in medium to low light situations?

3. can you use a DSLR as a point and shoot and have it auto focus?

4. if a DSLR camera has 3X optical zoom and I attach a zoom lense that is 5X optical zoom, does that mean I can have upto 15X optical zoom or is 5X the max?

5. how do you calculate the OZ? if a camera or lense is said to be 55-200mm, do you divide 200 by 55?

thanks for any answers you can provide. unfortunately I will probably have more later on. thanks alot!