feedback resistors in dual output

It is difficult to have good regulation for both 5V and 70V output because the voltage range is too big. Depending on the tolerance requirements of each channel, you may choose your architecture. One way of doing this, you can design the feedback circuit to regulate 5V channel. And add extra post regulation circuit to regulate 70V channel.

If we are usung without sensing feedback supply (70). then there is serios problem.There would not be overload protection and DPA will not be shut down if its over load or any othre fault comdition ,due to contiue over load the DPA will be damage. Have you any other solution?

You probably have to have protection circuit in the post regulation design for 70V channel.

Have you any design example?

I don't have a design example for that currently. If I found something useful for you later, I will share with you.