Thank you so much for all the replies! I really appreciate the help and all the wonderful advice!
Hopefully everything goes well, and for those that asked, he was insured and the seller is giving me a full refund. I just can’t stand to see him looking so broken if I can fix him. I figured if the horn repair doesn’t go well, and I got desperate I could always fill the hole where the horn goes and put a crystal or stone there instead; he wouldn’t be a unicorn, but still be pretty to look at…
Thanks again everyone!