Alright let Ross explain since you got that far. That is wave 6 not 5. Also the point of the I-worm as it says, it to separate the map, meaning the map "boss" is not that one small area, but there is more left of the I-worm. Basically your team has to split up into multiple groups.
Also Ross feels like Raid armor is not "fully deserved". This map is broken like mad. If rt3 would ever be released, it would come with the un-transing of a few mobs, and fixing the broken bombs (which is a huge game breaker.)
As per that half at wave 4, Ross only remembers saying there is a lot more not half. If he ever said half, it prob meant you are only half way done the map, as the last wave covers the entire map.