Is it Compatible with Space Exploration?

Yes, it goes as far as it requires Space Exploration

Is it compatible with Krastorio 2 + Space Exploration ?

It took some time and YES it is compatible with both, if i havent missed a thing.

Could there be some clarification on what the numbers describing the different breeding cycles mean in game?
For example the UraniUm Cell Process it usually has 8 GJ, while breeding it still has 8GJ but only 30% of the energy are conversed into Steam, the rest of the fission is going into indegriedents to enrich them which also requires neutrons and thus costing nuclear energy. So 30% is Steam energy and 70% is used to enrich products.

Is it fun?

Definitley.