I have a semi-related question I've always wanted to ask an expert. Is there any evidence that multi-cellular life evolved more than once? If not, do you lean one way or the other on the likelihood of it evolving more than once?

Not the OP but yes there’s plenty of evidence (overwhelming really). The sponge lineage that turned into the gastrointestinal tract of animals evolved separately from the plants that developed from charophyte algae. Fungi also became multicellular in parallel, but we’re not really sure what the original eukaryote was.