Christian, you seem like you are wanting to do things the right way and have a lot of questions. I've only been chasing since 2006 and one thing I realized was that until I got out there there were a lot more questions I didn't know that needed to be asked. Books are great and Tim V's are some of the best but there's not a book out there that can ever replace chasing with someone who has been doing it for a while. You will learn a whole lot more in a much shorter time if you combine reading books, watching videos, and chasing with an experienced chaser. If you don't know anyone who can help, there are some great tour outfits.
It's one thing to keep your distance, but it's another thing to know HOW to keep your distance. It is possible to be at a safe distance from one tornado and another one touch down closer. Go to Convective Addiction's website and order
Bullseye Bowdle and see what kind of trouble knowledgeable and experienced chasers can get into. Tornadoes can be hypnotizing and they can be moving at speeds much greater than it looks like.
Also, often a tornado will be rain wrapped posing another not-so-obvious hazard. That rain shaft that you drive into might have a surprise in store for you. And a tornado in it's rope stage can move very erratically as it is pushed around by RFD.
Another thing to consider is that tornadoes don't always have a condensation funnel all the way to the ground. And many of these can be powerful enough to pose a threat to your safety in a vehicle. You have to know what you are looking at, where you are in relation to the storm, etc... And the radar software has it's limitations as well. It takes 4 1/2 to 6 minutes for a WSR-88 radar to make a complete sweep, so your image might be that old or older. Lots can change in that amount of time. Take May 10 of this year, the Wakita/Medord tornado was about 5 miles ahead of the hook echo due to the storm motion being over 60MPH.
I'm not trying to discourage you from chasing, but rather encourage you to get some help learning the ropes. It will help you find the tornadoes, stay safe, and have more fun in the long run.