Sadly, the eggs are unlikely to be fertile, Ive had the same thing happen (different species though) and they never hatched, and yes that is egg laying behavior
Yes, male beetles are often ridiculously zealous and may mate with anything that even slightly resembles a female. On bugguide there are a few pics of various mistaken-identity copulations.
I had a small male fuzzy darkling beetle attempt to mate with a large velvet ant. Presumably because he thought she was the biggest, sexiest fuzzy darkling ever. The velvet ant was not pleased with his repeated attempts to climb on her back and always ran away while he chased after her.