I was afraid of him swallowing substrate and becoming impacted. He's on plain aspen but I've read lots of posts saying it's still safer to feed them in a substrate-free environment. Also the tutorials and things I've read have said that 90-95 is suitable but I'll keep that in mind. I'm thinking I'll try again Saturday based on what his previous owner said and your advice.
That being said if anyone else has more tips I'm still very much open to them!