I wouldnt be to concerned with his eating patterns or quantity at this age. Remember his stomach is the size of his clenched fist, so he might not eat more than this amount in a sitting. Children tend to eat smaller more frequent meals, so offer 5 meals a day. His milk intake sounds okay to me to. As long as you keep offering the good stuff, he will eventually start eating properly as he gets older, just dont fall into the trap of offering quick, non-nutritious meals just to get him to eat something. I have always been told that if they are hungry they will eat, and eat what they require, they wont starve themselves. It can also take 2 to 3 weeks after sickness for eating to come back.

Another question I have those is the lactose intolorance, what age was he when it started and what formula were you using? The reason I ask is that lactose intolerance that is started by a sickness such as gastro can hang around for quite sometime, and sometimes unless treated strictly can go away slower or have relapses. DD1 was diagnosed at 7mths and began on lactose free formula, this slowly became not good enough and she was put on soy products by 10 mths. She had to stay strictly on complete no dairy, even the slightess bit of dairy would upset her and the dr said doing this was preventing her system from repairing itself properly. We trialled her on small amounts at 12 mths, still a problem but again at 15 and she was fine, now a dairy eating queen. Dr said most children will stay lactose intolerance to at least 1, some even 2 or 3.

If you are really concerned about their food intake, try hiding fruit and vegies in things, purees can me mixed into things like mash, fruit blended into milk etc.