You shouldn't lose an ASN or PI block, they are registered to you at RIPE, only managed by the LIR and can be transferred to another LIR in exceptional or routine circumstances. I think you'll have to pay another fee though.

A PA block is just part of a LIR's block that they give you permission to use, so I doubt you could keep that if they went out of business, but maybe RIPE has a procedure for it.

For a hobbyist it’s perfectly fine, I think? I’ve been doing this for years. If I was a major corporation I might be more concerned.