I suggest that you do normal things like talking to him everyday and giving him some tomato juice too. You can by it at the Sundae Inn everyday, but Sunday (so on Saturday I'd double up if I were you.)
-To save some money you can plant tomatoes in summer and save them up and buy a blender to make your own tomato juice too.
You can also find the recipe for tomato risotto which I think is: tomatoes, onions, and rice. I'd check here to make sure though: http://www.gamershell.com/faqs/harvestmoontreeoftranquilityrecipelist/2.2.0/
It shouldn't take long to get his heart up at all.