Space?

Depending on strain, you could blow this room out, resulting in you having to choose violence! Some OG phenos will stretch to a min 2.5x in size, and it'll happen really fast. Most of those are looking real good for their age and as mentioned you could flip these within the next week. Definitely going to be some juggling for space, but thats a first world problem mate..you got this!

yea, it should fill in at this point. you will double the canopy size at minimum. Reconsider where that duct is... that's prime real estate for light. if you sacrifice a large area for a duct, make it along side or in corner. should be another way to route it without sacrificing one of the best areas for light or sacrificing any area for that matter.

Depends on the strain and if its a photo or auto. Either way id say you will be fine plenty of scrog there to re-route anything.

Would wait max. another week befor sending them into flowering. Also depends on how much they Strech + Sativa or Indica genetic

Very likely.