Can you use a 1 gallon jug or does it have to be a 2 liter. Will it still be enough humidity for growth. If you did not wet the cake before putting into terrarium will it still grow.
as long as your holes are good and the perlite lvl is ok you should be fine no matter what size you use.
as for not dunking, Im not sure i always dunk my cakes, tho i have gotten .5oz dried off 8 cakes invitro so im sure theres enough water for a flush of some sort.