The law is complex, but not vindictive.

You choosing to host that material is illegal. You finding yourself hosting that and taking action to remove it and aid the authorities, is not.

If I slip illegal content into your bag, the law may challenge your possession of that content, but if you can show you had no knowledge of possessing it and no intent to distribute and that in fact you've been setup, the law is going to treat you very differently to you obtaining that material and putting it in your bag yourself.

Servers aren't much different. It's what you do when you notice the problem that counts.

Which percentage of your life are you willing to bet on the fact that a judge will come to the correct understanding of how the fediverse works and that your understanding of the law is correct in the eyes of the judge. This ignores the enormous cost you will have to bear regardless of the outcome of the case.

These are serious offences and you should take them seriously.

The burden of proof proving that you didn't know is on you. Good luck proving a negative.