Glad you like the game :-) You can not remove radiation damage, but damage is only dealt as long as the crew is exposed to radiation. Check the camp stats before and after upgrading the shelter. Never heard of the game with the wilderness you mentioned, but sounds interesting.
I managed to finish the game with 2 stars. I can probably get one more on another play through. Can you tell me what the biology, and other skills do? I had biology maxed out but it did not appear to give me any bonus to food production? Can you have 3 greenhouses running while everything else is powered? It does not seem there will be enough power.
The game i think this is similar to is 'Help Will Come Tomorrow"