C.W.
Hi A.,
You might try keeping some mashed potatoes available for him along with his dinner meal. I think you are right- if he is a big boy- he most likely is hungry- so I would try substuting solids at nite- most kids that age like to eat with their fingers- so give him a few green beens- or other finger foods (ignore the mess) and give him the stage 3 if he is still acting like he wants more..... or if you are uncomfortable with that- try putting cereal in his nitetime bottle.
If this does not work for you- it is possible he could be teething.
good luck
blessings