My DD (18.5 mo) also doesn't chew her food very well. I asked our ped about it at her 18 mo appt and basically her advice was to keep waiting for all her teeth to come in (has all her molars, but only two eye teeth and no canines) and give her foods she has to chew, like crackers (great diet!). Not so helpful, huh? We usually just encourage her by singing silly songs; 'bite and chew, bite and chew.' Doesn't always work, but she seems to be getting a little better.
I also hear/feel DD fart in the middle of a NW, but I'd more likely credit it to the crying/screaming. I believe they still swallow air during that. I could be wrong, though. Maybe it's worth a try to do a few days of changing her diet and see if that makes a difference. It looks like her routine is right on track. It could be those bottom molars too. They were tough for us!