Ask-a-Dave's-Gardener: Hibiscus Help! Please help me save my hibiscus!!!, 1 by dmoroark

dmoroark wrote:
I have a hibiscus that I was going to give to a friend whom I cared for deeply. We parted ways, and during a deep depression I let the poor plant waste away. As I recover, I\'ve realized that this plant is very important to me, and I\'m doing my best to revive it. Will you please help me?

As much information as I can think of:
This past winter killed most of the original stems, but the roots from one of the plants survived, and new growth began.
Moving trauma and what I believe to have been wilt disease almost killed the new stuff
i repotted the plant in new soil, and gave it a liquid copper treatment.
plant has revived, but the soil was 30% nitrogen. I should have known better than to use it, but I was in a hurry to get it out of the old soil. Now, I think the plant has chemical burn. The soil is slow release.
the roots were thick. possibly too thick for the current pot.
I\'ve included a picture.

I want to repot in soil that is more suited to the plant and possibly trim the roots, but I don\'t want to stress the plant further.

What is your advice?