Rebuilding a hearth for my Insert

As I was preparing for my insert installation, I noticed a few things, some seem like a problem. The hacks that put in the wood burning fireplace cut out a good portion of the already undersized 2 x 8 floor joists, and made concrete forms for the hearth with some 1 x material. The concrete is not level, and has a large crack opening at the top side.

My plans are to remove the concrete hearth, and to reframe my floor structure to create two beam joists on either side, and to create a beam that will accept the joists that will end before the hearth area.

The question is, how would you guys recommend building the hearth up. I have a 22"x70"x2-1/4" Limestone hearth being made right now. The plan is to have the limestone's bottom to be level with the finished floor (white oak flooring).

The Kuma Sequoia should be arriving soon, and I would like to get the house ready to handle that beast.

Thanks,
Matt

Talked to Mark at Kuma Stoves. He told me that the insert only requires ember protection.

The main part of my question was to look for recommendations on how to create the structure for this application. I am not completely sure it is best to have any wood under the hearth at all.

One thought I had was to drill into the masonry wall, place rebar in the wall, and to thru-bolt some angle iron into the beam parallel to the wall to support a new concrete pad. Then create a galvanized pan to act as a form and heat shield for the hearth.

I thought someone may have been in my position before, and could point me in the right direction. Hopefully I am being descriptive enough to explain what I need to solve.