S.S.
I would set up a "grazing table" for him... finger snacks on a short table so that he could eat when the mood strikes..
i.e. grilled chicken fingers (seriously thin - 3inches long and 1/3 - 1/2 inch square... the texture will break apart for him) steamed baby carrots cut into slivers, yogurt, applesauce.
I'd also switch back to infant formula (if you've already gone to milk) - they have formula for babies older than 9 months that helps with vitamins, calories, and stuff.
Also, keep giving him new foods.. or even let him eat off your plate. It takes my sons 20 tries or more to get used to a new texture, and my oldest (4) still will not eat meat unless it's put through a blender first (i.e. spaghetti sauce, sloppy joe, chicken salad). He just doesn't like the texture.
BTW, how is your son's nose? Does he seem to be (or was he for a couple of months or more) a mouth breather? They hate to chew - they're accustomed to having to keep their mouth free to breathe.
S.