Here's an up close of the leaves, the trunk does have thorns.

Here is the base. Not sure what to think here, could the dead part be the tree and the green growth be rootstock? I have not found any graft line and before I pot this thing up with a new mix, I want to make sure its worth the effort of keeping it around.

That's all rootstock!
The original variety is the dead stump, with the original graft line just below where the dead twigs join the stump.
You are growing a trifoliate hybrid - probably a citrange or citrumelo. While it will never give you very edible citrus fruits, it is an interesting plant which will survive much more frost than a normal citrus. Depending on your zone, it might be possible to grow outside and will eventually produce ornamental fruits.

Thanks, and I was afraid of that. Not worth keeping around as it wont survive outside in this zone.

You could always graft something else in. I'm sure there's plenty of people around your area with budwood.

Actually, Mike, it probably would survive in zone 7. Citrange has been growing similar cultivars in his zone successfully. They do make a very pretty ornamental tree, btw. And, you can use it for rootstock grafting as well. I would say keep it, plant it outside in the warmest, most protected area of your home and see how it does.

Patty S.

Plant that thing outside! You never know.

Some of us are growing Citrandarin and Citrumelo in the ground here in the DC area. Citrange should do OK too.