There are three airports in metro Osaka. International would be KIX. Then it would be train+train (Haruka+Shinkansen) and not bus+train.

AA may not show the 19:30 HND-HIJ JL flight but you should be able to book it. The HIJ-JR Hiroshima limo bus is not that bad. It should go to other downtown location too. Just remember not to jump into the first cab you see.

The HIJ is built on top of a hill with a runway extension over a cliff, kind of like flying into SAN. It will be dark by the time you get there.