Doubt in Regression

Warm Greeting to all!

I have some doubts in my Regression model. I explained below. Please
give me a conclusion on my problem and show me the right way to get the
solution.

Thanks,

Lawrence.

First Problem:

1-Extremely Frustrating
2-Very Frustrating
3-Somewhat Frustrating
4-Neutral
5-Somewhat Good
6-Very Good
7-Extremely Good
8-Unsure/Not applicable

This is my independent variable scale structure. I want to see the
contribution of this kind of independent variables with dependent
variable(5 point scale -Satisfaction). Before running multiple linear
regression analysis I created new set of variables for independent
variables without Unsure/Not applicable option. After done this action
I am getting 40% of system missing in my data files. But I don't want
to loss this much information from my analysis and I want use all the
cases. I know some of the options like Series Mean, Replacing with near
mean or median and interploation methods are available for replacing
system missing. Can I use which method for my problem and it can be
effective? explain.....

Second Problem:
All my independent variables are significantly
correlated together with 99% significance level. What can I do? This
model R-Square value is .35 and I am used Backward method. I lossed
some variables when I seen last model. I classified my independent
variable into three groups. I want to see how the first group
contribute the dependent variable and in the same way for remaining 2
groups. And also how this 15 attributes contribute dependent variable.
Here is the flow diagram.


|<------Group 1<------- 5 attributes
|
|
Dependent<----- <------Group 2<------- 5 attributes
|
|
|<------Group 3<------- 5 attributes

.