He sounds like he's going to be a great friend! I would feed a higher quality kibble- he'll be able to get more nutritional value from something else with less processed stuff in it. The amount you end up feeding him will depend a lot on the kibble, but I wouldn't recommend Iams. I personally feed Taste of the Wild to my hard-to-keep-weight-on dog, but that's simply because he is so sensitive that it's the only thing he's done well on, and it's pretty affordable. There is a ton of information in the feeding forum about what foods people recommend and why- different foods work well for different dogs (and budgets).
He is gorgeous