Insulate basement

[Krewlir]

I have a 70s split-level house where I'm going to renovate the partial basement.
Today, it's an uninsulated poured slab with tar on it. There’s a kind of framework with loose fill and then rough sheathing and parquet flooring. I'm considering tearing all this out as it doesn’t seem like a good solution. I'm also thinking about underfloor heating to get rid of the radiators.

The plan is to remove the tar, or should it stay?
Then lay 100 mm of foam insulation and pour 50-60mm with reinforcement. Then lay waterborne underfloor heating and pour up another 30cm. After that, I thought about Platon and parquet.

Is this a good idea or is there a better solution? Is 100 mm of insulation enough to avoid having to demolish, and is it okay to cast it between the concrete? Should there be some plastic somewhere?

Thanks in advance!

 

[Sesulo]

Completely novice but... I assume the tar is to counteract ground moisture from below and should perhaps be replaced with a modern solution (platon).

Then there is some debate about underfloor heating on an uninsulated slab (cellplast) as you can get reverse moisture migration during certain seasons.

The safest thing is probably to break it up and completely redo the slab.