Playing as a mycus

So… i finally became one with the fungi from Yuggoth or netherium or wherever… but i have some HARD problems.
First - i am not even resistant to fungal infections?! I still need to keep my gas mask on, or my torso keeps getting hurt and i vomit grey goo. For some reason though - my NPC just stands there, never attacks my fungal friends and never shows any signs of illness. I guess i’ll force feed him some Marloss later - he shall join us. Still, getting infected with fungi, while being a fungus seems weird.
Second - no mycus mutations except Mycus feeder. I keep eating and eating the fruit but nothing happens - what should i do?
So… can anyone tell me if my issues are bugs? Or am i doing something wrong? Could other Mycus players tell me how they play the game?
Thanks in advance.

You’ll get more as you go along. You mutate in your sleep.