Hello Dani!
Try to be a bit more specific with the questions you are asking, to generate more specific answers. I too have had back problems (due to herniated disc at age 28) but I have never had problems with my feet. Fortunately, due to extensive research and very dedicated training, I have completely overcome the herniated disc and very seldom have any lower back problems these days!
For balance, stand on one leg for extended periods of time, alternating legs of course. Try to accomplish everyday tasks while standing on one leg. While standing on one leg, slowly extend various kicks, working to maintain proper form during execution. When you reach the completely extended position, try to hold that position for as long as you possibly can. You can use a chair, wall or railing for assistance in the early stages of this training exercise. Also, when I was younger I used to walk railroad tracks all the time, staying on the track as long as possible without losing my balance. A balance beam is great if you have access to one. If not, one can be made for very little money!
Energy/sensitivity training is the hardest thing to do on your own. You can use some type of springarm or spring loaded device to gain some sensitivity, but a knowledgeable training partner of Sifu is the best thing for this area of training! The most important drills are don chi sao and seong chi sao.
All of these questions and more will be answered when you receive the package that is coming your way!
Keep Blasting!
Sifu Lamar M. Davis II
Senior Instructor
Hardcore Jeet Kune Do
Sifu@HardcoreJKD.com
http://www.HardcoreJKD.com
http://www.RealCombatOnline.com
Phone (205) 956-1901
"Hit Hard, Hit Fast, Hit First - ALWAYS!"